Positive resist composition and method of forming resist pattern

ABSTRACT

A positive resist composition including a resin component (A) which exhibits increased alkali solubility under action of acid and an acid-generator component (B) which generates acid upon exposure,
         the resin component (A) including a structural unit (a0-1) represented by general formula (a0-1) shown below and a structural unit (a0-2) represented by general formula (a0-2) shown below:       

     
       
         
         
             
             
         
       
     
     wherein: R represents a hydrogen atom, a halogen atom, a lower alkyl group or a halogenated lower alkyl group; each of Y 1  and Y 3  independently represents an aliphatic cyclic group; Z represents a tertiary alkyl group-containing group or an alkoxyalkyl group; a represents an integer of 1 to 3, and b represents an integer of 0 to 2, such that a+b=1 to 3; each of c, d and e independently represents an integer of 0 to 3; each of g and h independently represents an integer of 0 to 3; and i represents an integer of 1 to 3.

TECHNICAL FIELD

The present invention relates to a positive resist composition and amethod of forming a resist pattern.

Priority is claimed on Japanese Patent Application No. 2006-145285,filed May 25, 2006, and Japanese Patent Application No. 2006-244293,filed Sep. 8, 2006, the contents of which are incorporated herein byreference.

BACKGROUND ART

In lithography techniques, for example, a resist film composed of aresist material is formed on a substrate, and the resist film issubjected to selective exposure of radial rays such as light or electronbeam through a mask having a predetermined pattern, followed bydevelopment, thereby forming a resist pattern having a predeterminedshape on the resist film. A resist material in which the exposedportions become soluble in a developing solution is called apositive-type, and a resist material in which the exposed portionsbecome insoluble in a developing solution is called a negative-type.

In recent years, in the production of semiconductor elements and liquidcrystal display elements, advances in lithography techniques have led torapid progress in the field of pattern miniaturization.

Typically, these miniaturization techniques involve shortening thewavelength of the exposure light source. Conventionally, ultravioletradiation typified by g-line and i-line radiation has been used, butnowadays KrF excimer lasers and ArF excimer lasers are now starting tobe introduced in mass production of semiconductor elements. Furthermore,research is also being conducted into lithography techniques that use anexposure light source having a wavelength shorter than these excimerlasers, such as F₂ excimer lasers, electron beam, extreme ultravioletradiation (EUV), and X ray.

Resist materials for use with these types of exposure light sourcesrequire lithography properties such as a high resolution capable ofreproducing patterns of minute dimensions, and a high level ofsensitivity to these types of exposure light sources. As a resistmaterial which satisfies these conditions, a chemically amplified resistis used, which includes a base resin that exhibits a changed alkalisolubility under action of acid and an acid generator that generatesacid upon exposure. For example, a chemically amplified positive resistcontains, as a base resin, a resin which exhibits increased alkalisolubility under action of acid, and an acid generator. In the formationof a resist pattern, when acid is generated from the acid generator uponexposure, the exposed portions become alkali soluble.

Currently, chemically amplified resins that contain structural unitsderived from (meth)acrylate esters within the main chain (acrylicresins) are widely used as base resins for resists that use ArF excimerlaser lithography, as they exhibit excellent transparency in thevicinity of 193 nm (for example, see Patent Document 1). Further, asacrylic resins for use in such application, those which have astructural unit derived from (meth)acrylate ester having an aliphaticpolycyclic group such as an adamantane skeleton at the ester portion aregenerally used, as they exhibit excellent transparency in the vicinityof 193 nm and excellent dry-etching resistance.

Further, for improving the lithography properties, those which haveplurality of structural units are currently used as the base resincomponent of chemically amplified resists. For example, a positiveresist has a structural unit containing an acid dissociable, dissolutioninhibiting group which is dissociable under action of acid generatedfrom the acid generator, and also has a structural unit containing apolar group such as a hydroxyl group, a structural unit containing alactone structure, and the like. In particular, a structural unitcontaining a polar group is widely used, as it enhances the affinity ofthe resist for an alkali developing solution, and contributes toimprovement in the resolution. For example, in an acrylic resin, a(meth)acrylate ester having a hydroxyl group-containing aliphaticpolycyclic group at the ester portion, such as a structural unit derivedfrom hydroxyadamantyl (meth)acrylate, is generally used.

Here, the term “(meth)acrylic acid” is a generic term that includeseither or both of acrylic acid having a hydrogen atom bonded to theα-position and methacrylic acid having a methyl group bonded to theα-position. The term “(meth)acrylate ester” is a generic term thatincludes either or both of the acrylate ester having a hydrogen atombonded to the α-position and the methacrylate ester having a methylgroup bonded to the α-position. The term “(meth)acrylate” is a genericterm that includes either or both of the acrylate having a hydrogen atombonded to the α-position and the methacrylate having a methyl groupbonded to the α-position.

[Patent Document 1] Japanese Unexamined Patent Application, FirstPublication No. 2003-241385

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

However, as such base resins have a polar group such as a hydroxylgroup, such base resins are disadvantageous in that they exhibit poorsolubility in an organic solvent. Such poor solubility of the base resinin an organic solvent causes disadvantages such as labor and time inpreparation of a resist solution, low stability of a resist solutionprepared, and the like. Further, problems are caused in the synthesis ofthe base resin. For example, when synthesis of a resin is conductedusing a monomer exhibiting high polarity, such as the aforementionedhydroxyadamantyl (meth)acrylate, the viscosity of the generated polymerbecomes higher as the amount of the monomer added is increased, andhence, it becomes difficult to purify the generated polymer. Therefore,there is a large limitation in the amount of the monomer exhibiting highpolarity, such as hydroxyadamantyl (meth)acrylate.

For avoiding the aforementioned problem, the use of a resin which doesnot have a structural unit containing a polar group has been considered.However, when such a resin is used, the shape of a resist pattern formedis deteriorated.

The present invention takes the above circumstances into consideration,with an object of providing a positive resist composition which exhibitsexcellent solubility in an organic solvent and is capable of forming aresist pattern having an excellent shape, and a method of forming aresist pattern.

Means for Solving the Problems

As a result of extensive studies, present inventors have found that theaforementioned problems can be solved by using a resin containing twospecific structural units. The present invention has been completed,based on this finding.

Specifically, a first aspect of the present invention is a positiveresist composition including a resin component (A) which exhibitsincreased alkali solubility under action of acid and an acid-generatorcomponent (B) which generates acid upon exposure,

the resin component (A) including a structural unit (a0-1) representedby general formula (a0-1) shown below and a structural unit (a0-2)represented by general formula (a0-2) shown below:

wherein:in general formula (a0-1), R represents a hydrogen atom, a halogen atom,a lower alkyl group or a halogenated lower alkyl group; Y¹ represents analiphatic cyclic group; Z represents a tertiary alkyl group-containinggroup or an alkoxyalkyl group; a represents an integer of 1 to 3, and brepresents an integer of 0 to 2, such that a+b=1 to 3; and each of c, dand e independently represents an integer of 0 to 3, andin general formula (a0-2), R represents a hydrogen atom, a halogen atom,a lower alkyl group or a halogenated lower alkyl group; Y³ represents analiphatic cyclic group; each of g and h independently represents aninteger of 0 to 3; and i represents an integer of 1 to 3.

A second aspect of the present invention is a method of forming a resistpattern, including: applying a positive resist composition of the firstaspect to a substrate to form a resist film on the substrate; subjectingthe resist film to exposure; and developing the resist film to form aresist pattern.

In the present description and claims, the term “structural unit” refersto a monomer unit that contributes to the formation of a resin component(polymer).

An “alkyl group” includes linear, branched or cyclic, monovalentsaturated hydrocarbon, unless otherwise specified.

An “alkylene group” includes linear, branched or cyclic, divalentsaturated hydrocarbon, unless otherwise specified.

A “lower alkyl group” is an alkyl group of 1 to 5 carbon atoms.

The term “exposure” is used as a general concept that includesirradiation with any form of radiation.

EFFECTS OF THE INVENTION

According to the present invention, there are provided a positive resistcomposition which exhibits excellent solubility in an organic solventand is capable of forming a resist pattern having an excellent shape,and a method of forming a resist pattern.

BEST MODE FOR CARRYING OUT THE INVENTION

<<Positive Resist Composition>>

The resist composition of the present invention includes a resincomponent (A) (hereafter, frequently referred to as “component (A)”)which exhibits increased solubility in an alkali developing solutionunder action of acid and an acid-generator component (B) which generatesacid upon irradiation.

In the positive resist composition, the component (A) is alkaliinsoluble prior to exposure, and when acid is generated from thecomponent (B) upon exposure, the generated acid acts on the component(A) to increase the alkali solubility thereof. Therefore, in theformation of a resist pattern, by conducting selective exposure of aresist film formed by applying the positive resist composition onto asubstrate, the exposed portions become alkali soluble, whereas theunexposed portions remain alkali insoluble, and hence, a resist patterncan be formed by alkali developing.

<Component (A)>

In the present invention, the component (A) includes a structural unit(a0-1) represented by general formula (a0-1) above and a structural unit(a0-2) represented by general formula (a0-2) above.

Both of the structural unit (a0-1) and the structural unit (a0-2) arestructural units derived from acrylate ester.

In the present descriptions and claims, the term “structural unitderived from an acrylate ester” refers to a structural unit which isformed by the cleavage of the ethylenic double bond of an acrylateester.

The term “acrylate ester” is a generic term that includes acrylateesters having a hydrogen atom bonded to the carbon atom on theα-position, and acrylate esters having a substituent (an atom other thana hydrogen atom or a group) bonded to the carbon atom on the α-position.With respect to the “structural unit derived from an acrylate ester”,the “α-position (the carbon atom on the α-position)” refers to thecarbon atom having the carbonyl group bonded thereto, unless specifiedotherwise.

As the substituent which may be bonded to the carbon atom on theα-position (substituent at the α-position), a halogen atom, a loweralkyl group or a halogenated lower alkyl group can be mentioned.

Examples of halogen atoms for the substituent at the α-position includefluorine atoms, chlorine atoms, bromine atoms and iodine atoms, andfluorine atoms are particularly desirable.

Examples of the lower alkyl group for the substituent at the α-positioninclude linear or branched lower alkyl groups such as a methyl group,ethyl group, propyl group, isopropyl group, n-butyl group, isobutylgroup, tert-butyl group, pentyl group, isopentyl group, and neopentylgroup.

Examples of the halogenated lower alkyl group for the substituent at theα-position include groups in which a part or all of the hydrogen atomsof the aforementioned “lower alkyl group for the substituent at theα-position” are substituted with halogen atoms. Examples of halogenatoms include fluorine atoms, chlorine atoms, bromine atoms and iodineatoms, and fluorine atoms are particularly desirable.

In the present invention, it is preferable that a hydrogen atom, ahalogen atom, a lower alkyl group or a halogenated lower alkyl group bebonded to the α-position of the acrylate ester, more preferably ahydrogen atom, a fluorine atom, a lower alkyl group or a fluorinatedlower alkyl group. In terms of industrial availability, a hydrogen atomor a methyl group is particularly desirable.

[Structural Unit (a0-1)]

In general formula (a0-1), R represents a hydrogen atom, a halogen atom,a lower alkyl group or a halogenated lower alkyl group.

The halogen atom, lower alkyl group and halogenated lower alkyl groupfor R are the same as the halogen atom, lower alkyl group andhalogenated lower alkyl group which may be bonded to the α-position ofthe aforementioned acrylate ester. As R, a hydrogen atom or a methylgroup is preferable.

In general formula (a0-1), Y¹ represents an aliphatic cyclic group.

In the present description and claims, the term “aliphatic” is arelative concept used in relation to the term “aromatic”, and defines agroup or compound that has no aromaticity. The term “aliphatic cyclicgroup” refers to a mono cyclic group or polycyclic group that has noaromaticity.

The “aliphatic cyclic group” within the structural unit (a0-1) may ormay not have a substituent. Examples of substituents include a loweralkyl group of 1 to 5 carbon atoms, a fluorine atom, a fluorinated loweralkyl group of 1 to 5 carbon atoms which is substituted with a fluorineatom, and an oxygen atom (═O).

The basic ring of the “aliphatic cyclic group” exclusive of substituents(aliphatic ring) is not limited to be constituted from only carbon andhydrogen (not limited to hydrocarbon rings), but is preferably ahydrocarbon ring. Further, the “hydrocarbon ring” may be eithersaturated or unsaturated, but is preferably saturated. The aliphaticcyclic group may be either a polycyclic group or a monocyclic group.

As such aliphatic cyclic groups, groups in which two or more hydrogenatoms have been removed from a monocycloalkane or a polycycloalkane suchas a bicycloalkane, tricycloalkane or tetracycloalkane which may or maynot be substituted with a lower alkyl group, a fluorine atom or afluorinated lower alkyl group, may be mentioned. Specific examplesinclude groups in which two or more hydrogen atoms have been removedfrom a monocycloalkane such as cyclopentane and cyclohexane; and groupsin which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane.

The aliphatic cyclic group within the structural unit (a0-1) ispreferably a polycyclic group, and a group in which two or more hydrogenatoms have been removed from adamantane is particularly desirable.

In general formula (a0-1), Z represents a tertiary alkylgroup-containing group or an alkoxyalkyl group.

In the present description and claims, the term “tertiary alkyl group”refers to an alkyl group having a tertiary carbon atom. As mentionedabove, the term “alkyl group” refers to a monovalent saturatedhydrocarbon group, and includes chain-like (linear or branched) alkylgroups and cyclic alkyl groups.

The term “tertiary alkyl group-containing group” refers to a group whichincludes a tertiary alkyl group in the structure thereof. The tertiaryalkyl group-containing group may be either constituted of only atertiary alkyl group, or constituted of a tertiary alkyl group and anatom or group other than a tertiary alkyl group.

As the “atom or group other than a tertiary alkyl group” whichconstitutes the tertiary alkyl group-containing group with a tertiaryalkyl group, a carbonyloxy group, a carbonyl group, an alkylene groupand an oxygen atom can be exemplified.

As the tertiary alkyl group-containing group for Z, a tertiary alkylgroup-containing group which does not have a ring structure, and atertiary alkyl group-containing group which has a ring structure can beexemplified.

A tertiary alkyl group-containing group which does not have a ringstructure is a group which has a branched tertiary alkyl group as thetertiary alkyl group, and has no ring structure in the structurethereof.

As the branched tertiary alkyl group, for example, a group representedby general formula (I) shown below may be exemplified.

In general formula (I), each of R²¹ to R²³ independently represents alinear or branched alkyl group. The alkyl group preferably has 1 to 5carbon atoms, more preferably 1 to 3.

Further, in the group represented by general formula (I), the totalnumber of carbon atoms is preferably 4 to 7, more preferably 4 to 6,most preferably 4 or 5.

Specific examples of groups represented by general formula (I) include atert-butyl group and a tert-amyl group, and a tert-butyl group ispreferable.

Examples of tertiary alkyl group-containing groups which do not have aring structure include the aforementioned branched tertiary alkyl group;a tertiary alkyl group-containing, chain-like alkyl group in which theaforementioned branched tertiary alkyl group is bonded to a linear orbranched alkylene group; a tertiary alkyloxycarbonyl group which has theaforementioned branched tertiary alkyl group as the tertiary alkylgroup; and a tertiary alkyloxycarbonylalkyl group which has theaforementioned branched tertiary alkyl group as the tertiary alkylgroup.

As the alkylene group within the tertiary alkyl group-containing,chain-like alkyl group, an alkylene group of 1 to 5 carbon atoms ispreferable, more preferably 1 to 4 carbon atoms, and still morepreferably 1 to 2 carbon atoms.

As a chain-Like tertiary alkyloxycarbonyl group, for example, a grouprepresented by general formula (II) shown below can be mentioned. Ingeneral formula (II), R²¹ to R²³ are as defined for R²¹ to R²³ ingeneral formula (I) above. As the chain-like tertiary alkyloxycarbonylgroup, a tert-butyloxycarbonyl group (t-boc) or a tert-amyloxycarbonylgroup are preferable.

As a chain-like tertiary alkyloxycarbonylalkyl group, for example, agroup represented by general formula (III) shown below can be mentioned.In general formula (III), R²¹ to R²³ are as defined for R²¹ to R²³ ingeneral formula (I) above. In general formula (III), f is an integer of1 to 3, preferably 1 or 2. As the chain-like tertiaryalkyloxycarbonylalkyl group, a tert-butyloxycarbonylmethyl group or atert-butyloxycarbonylethyl group are preferable.

Among these, as the tertiary alkyl group-containing groups which do nothave a ring structure, a tertiary alkyloxycarbonyl group or a tertiaryalkyloxycarbonylalkyl group is preferable, more preferably a tertiaryalkyloxycarbonyl group, and most preferably a tert-butyloxycarbonylgroup.

A tertiary alkyl group-containing group which has a ring structure is agroup which contains a tertiary carbon atom and a ring structure in thestructure thereof.

In the tertiary alkyl group-containing group which has a ring structure,the ring structure preferably has 4 to 12 carbon atoms which constitutethe ring, more preferably 5 to 10 carbon atoms, and most preferably 6 to10 carbon atoms. As the ring structure, for example, groups in which oneor more hydrogen atoms have been removed from a monocycloalkane or apolycycloalkane such as a bicycloalkane, tricycloalkane ortetracycloalkane may be mentioned. Preferable examples include groups inwhich one or more hydrogen atoms have been removed from amonocycloalkane such as cyclopentane and cyclohexane; and groups inwhich one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane.

As the tertiary alkyl group-containing group which has a ring structure,for example, a group having the following group (1) or (2) as thetertiary alkyl group can be mentioned.

(1) A group in which a linear or branched alkyl group is bonded to acarbon atom which constitutes the ring of a cyclic alkyl group(cycloalkyl group), so that the carbon atom becomes a tertiary carbonatom.(2) A group in which an alkylene group (branched alkylene group) havinga tertiary carbon atom is bonded to a carbon atom constituting the ringof a cycloalkyl group.

In the aforementioned group (1), the linear or branched alkyl grouppreferably has 1 to 5 carbon atoms, more preferably 1 to 4, and mostpreferably 1 to 3.

Specific examples of the group (1) include a 2-methyl-2-adamantyl group,a 2-ethyl-2-adamantyl group, a 1-methyl-1-cycloalkyl group and1-ethyl-1-cycloalkyl group.

In the aforementioned group (2), the cycloalkyl group having a branchedalkylene group bonded thereto may have a substituent. Examples of suchsubstituents include a fluorine atom, a fluorinated lower alkyl group of1 to 5 carbon atoms which is substituted with a fluorine atom, and anoxygen atom (═O).

As a specific example of the group (2), a group represented by generalformula (IV) shown below may be mentioned.

In general formula (IV), R²⁴ represents a cycloalkyl group which may ormay not have a substituent. Examples of the substituent which thecycloalkyl group may include a fluorine atom, a fluorinated alkyl groupof 1 to 5 carbon atoms which is substituted by a fluorine atom, and anoxygen atom (═O).

Each of R²⁵ and R²⁶ independently represents a linear or branched alkylgroup. As the alkyl group, the same as the linear or branched alkylgroup for R²¹ to R²³ in general formula (I) above may be mentioned.

As the alkoxyalkyl group for Z, for example, a group represented bygeneral formula (V) may be mentioned.

In formula (V), R⁴¹ represents a linear, branched or cyclic alkyl group.

When R⁴¹ is a linear or branched alkyl group, it is preferably an alkylgroup of 1 to 5 carbon atoms, more preferably an ethyl group or a methylgroup, and an ethyl group is particularly desirable.

When R⁴¹ is a cyclic alkyl group, it preferably has 4 to 15 carbonatoms, more preferably 4 to 12 carbon atoms, and most preferably 5 to 10carbon atoms. Examples thereof include groups in which one or morehydrogen atoms have been removed from a monocycloalkane or apolycycloalkane such as a bicycloalkane, tricycloalkane ortetracycloalkane, which may or may not be substituted with a fluorineatom or a fluorinated lower alkyl group. Specific examples includegroups in which one or more hydrogen atoms have been removed from amonocycloalkane such as cyclopentane and cyclohexane; and groups inwhich one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane. Among these, a group in which oneor more hydrogen atoms have been removed from adamantane is preferable.

R⁴² represents a linear or branched alkylene group. The alkylene grouppreferably has 1 to 5 carbon atoms, more preferably 1 to 3 carbon atoms,and most preferably 1 or 2.

As the alkoxyalkyl group for Z, a group represented by general formula(VI) shown below is particularly desirable.

In general formula (VI), R⁴¹ is as defined for R⁴¹ in general formula(V) above, and each of R⁴³ and R⁴⁴ independently represents a linear orbranched alkyl group or a hydrogen atom.

With respect to R⁴³ and R⁴⁴, the alkyl group preferably has 1 to 15carbon atoms, and may be either linear or branched. The alkyl group forR⁴³ and R⁴⁴ is preferably an ethyl group or a methyl group, and mostpreferably a methyl group. It is particularly desirable that either oneof R⁴³ and R⁴⁴ be a hydrogen atom, and the other be a methyl group.

Among the above-mentioned examples, as Z, a tertiary alkylgroup-containing group is preferable, more preferably a grouprepresented by general formula (II) above, and most preferably atert-butyloxycarbonyl group (t-boc).

In general formula (a0-1), a represents an integer of 1 to 3, and brepresents an integer of 0 to 2, with the proviso that a+b=1 to 3.

a is preferably 1.b is preferably 0.a+b is preferably 1.c represents an integer of 0 to 3, preferably 0 or 1, and morepreferably 0.d represents an integer of 0 to 3, preferably 0 or 1, and morepreferably 0.e represents an integer of 0 to 3, preferably 0 or 1, and morepreferably 0.

As the structural unit (a0-1), a structural unit represented by generalformula (a0-1-1) shown below is particularly desirable.

wherein R, Z, b, c, d and e are respectively as defined for R, Z, b, c,d and e in general formula (a0-1) above.

A monomer for deriving the structural unit (a0-1) can be synthesized,for example, by protecting a part or all of the hydroxyl groups within acompound represented by general formula (a0-1′) shown below (an acrylateester containing an aliphatic cyclic group having 1 to 3 alcoholichydroxyl groups) with tertiary alkyl group-containing groups oralkoxyalkyl groups by a conventional method.

wherein R, Y¹, a, b, c, d and e are respectively as defined for R, Y¹,a, b, c, d and e in general formula (a0-1) above.

As the structural unit (a0-1), one type of structural unit may be usedalone, or two or more types of structural units may be used incombination.

The amount of the structural unit (a0-1) within the component (A) basedon the combined total of all structural units constituting the component(A) is preferably 1 to 40 mol %, more preferably 1 to 25 mol %, andstill more preferably 5 to 20 mol %. By making the amount of thestructural unit (a0-1) at least as large as 1 mol %, the solubility ofthe component (A) in an organic solvent is improved. On the other hand,by making the amount of the structural unit (a0-1) no more than 40 mol%, a good balance can be achieved with the other structural units.

[Structural Unit (a0-2)]

As R in general formula (a0-2) above, the same as R in general formula(a0-1) above can be mentioned.

As the aliphatic cyclic group for Y³, the same as the aliphatic cyclicgroup for Y¹ in general formula (a0-1) above can be mentioned. As Y³, itis preferable that the basic ring (aliphatic ring) has the samestructure as Y¹.

g represents an integer of 0 to 3, preferably 0 or 1, and morepreferably 0.

h represents an integer of 0 to 3, preferably 0 or 1, and morepreferably 0.

i represents an integer of 1 to 3, and preferably 1.

As the structural unit (a0-2), a structural unit represented by generalformula (a0-2-1) shown below is preferable, and a structural unit inwhich one of the i groups of —(CH₂)_(h)—OH is bonded to the 3rd positionof the 1-adamantyl group is particularly desirable.

wherein R, g, h, and i are respectively as defined for R, g, h, and i ingeneral formula (a0-2) above.

As the structural unit (a0-2), one type of structural unit may be usedalone, or two or more types of structural units may be used incombination.

The amount of the structural unit (a0-2) within the component (A) basedon the combined total of all structural units constituting the component(A) is preferably 1 to 30 mol %, more preferably 5 to 25 mol %, andstill more preferably 10 to 20 mol %. By making the amount of thestructural unit (a0-2) at least as large as 1 mol %, the rectangularityof the cross-sectional shape of the resist pattern is improved, andhence, a resist pattern having an excellent shape can be formed. On theother hand, by making the amount of the structural unit (a0-2) no morethan 30 mol %, a good balance can be achieved with the other structuralunits.

[Structural Unit (a1)]

The component (A) preferably has a structural unit (a1) derived from anacrylate ester having an acid dissociable, dissolution inhibiting group,as well as the structural unit (a0-1) and the structural unit (a0-2).

As the acid dissociable, dissolution inhibiting group in the structuralunit (a1), any of the groups that have been proposed as aciddissociable, dissolution inhibiting groups for the base resins ofchemically amplified resists can be used, provided the group has analkali dissolution-inhibiting effect that renders the entire component(A) alkali insoluble prior to dissociation, and then followingdissociation, renders the entire component (A) alkali soluble.

Generally, groups that form either a cyclic or chain-like tertiary alkylester with the carboxyl group of the (meth)acrylic acid, and acetal-typeacid dissociable, dissolution inhibiting groups such as alkoxyalkylgroups are widely known.

The term “(meth)acrylic acid” is a generic term that includes either orboth of acrylic acid having a hydrogen atom bonded to the α-position andmethacrylic acid having a methyl group bonded to the α-position.

Here, a tertiary alkyl ester describes a structure in which an ester isformed by substituting the hydrogen atom of a carboxyl group with achain-like or cyclic tertiary alkyl group, and a tertiary carbon atomwithin the chain-like or cyclic tertiary alkyl group is bonded to theoxygen atom at the terminal of the carbonyloxy group (—C(O)—O—). In thistertiary alkyl ester, the action of acid causes cleavage of the bondbetween the oxygen atom and the tertiary carbon atom.

The chain-like or cyclic alkyl group may have a substituent.

Hereafter, for the sake of simplicity, groups that exhibit aciddissociability as a result of the formation of a tertiary alkyl esterwith a carboxyl group are referred to as “tertiary alkyl ester-type aciddissociable, dissolution inhibiting groups”.

Examples of tertiary alkyl ester-type acid dissociable, dissolutioninhibiting groups include aliphatic branched, acid dissociable,dissolution inhibiting groups and aliphatic cyclic group-containing aciddissociable, dissolution inhibiting groups.

The term “aliphatic branched” refers to a branched structure having noaromaticity.

The “aliphatic branched, acid dissociable, dissolution inhibiting group”is not limited to be constituted of only carbon and hydrogen (notlimited to hydrocarbon groups), but is preferably a hydrocarbon group.

Further, the “hydrocarbon group” may be either saturated or unsaturated,but is preferably saturated.

Examples of aliphatic branched, acid dissociable, dissolution inhibitinggroups include tertiary alkyl groups of 4 to 8 carbon atoms, andspecific examples include a tert-butyl group, tert-amyl group andtert-heptyl group.

In the “aliphatic cyclic group-containing acid dissociable, dissolutioninhibiting group”, the “aliphatic cyclic group” may or may not have asubstituent. Examples of substituents include a lower alkyl group of 1to 5 carbon atoms, a fluorine atom, fluorinated lower alkyl groups of 1to 5 carbon atoms which is substituted with a fluorine atom, and anoxygen atom (═O).

The basic ring of the “aliphatic cyclic group” exclusive of substituentsis not limited to be constituted from only carbon and hydrogen (notlimited to hydrocarbon groups), but is preferably a hydrocarbon group.Further, the “hydrocarbon group” may be either saturated or unsaturated,but is preferably saturated. Furthermore, the “aliphatic cyclic group”is preferably a polycyclic group.

As such aliphatic cyclic groups, groups in which one or more hydrogenatoms have been removed from a monocycloalkane or a polycycloalkane suchas a bicycloalkane, tricycloalkane or tetracycloalkane which may or maynot be substituted with a lower alkyl group, a fluorine atom or afluorinated lower alkyl group, may be exemplified. Specific examplesinclude groups in which one or more hydrogen atoms have been removedfrom a monocycloalkane such as cyclopentane and cyclohexane; and groupsin which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane.

As the aliphatic cyclic group-containing acid dissociable, dissolutioninhibiting group, for example, a group which has a tertiary carbon atomon the ring structure of the cycloalkyl group can be mentioned. Specificexamples include a 2-methyl-2-adamantyl group and a 2-ethyl-2-adamantylgroup. Further, groups having an aliphatic cyclic group such as anadamantyl group, and a branched alkylene group having a tertiary carbonatom bonded thereto, as in the group bonded to the oxygen atom of thecarbonyloxy group (—C(O)—O—) in the structural units represented bygeneral formula (a1″) shown below, can be exemplified.

wherein R is as defined for R in general formula (a0-1) above, and eachof R¹⁵ and R¹⁶ represents an alkyl group (which may be either linear orbranched, and preferably has 1 to 5 carbon atoms).

An “acetal-type acid dissociable, dissolution inhibiting group”generally substitutes a hydrogen atom at the terminal of analkali-soluble group such as a carboxy group or a hydroxyl group, so asto be bonded with an oxygen atom. When acid is generated upon exposure,the generated acid acts to break the bond between the acetal-type aciddissociable, dissolution inhibiting group and the oxygen atom to whichthe acetal-type, acid dissociable, dissolution inhibiting group isbonded.

Examples of acetal-type acid dissociable, dissolution inhibiting groupsinclude groups represented by general formula (p1) shown below.

wherein R¹′ and R²′ each independently represents a hydrogen atom or alower alkyl group; n represents an integer of 0 to 3; and Y represents alower alkyl group or an aliphatic cyclic group.

In general formula (p1) above, n is preferably an integer of 0 to 2,more preferably 0 or 1, and most preferably 0.

As the lower alkyl group for R¹′ and R²′, the same as the lower alkylgroups for R above can be mentioned. As the lower alkyl group for R¹′and R²′, a methyl group or ethyl group is preferable, and a methyl groupis particularly desirable.

In the present invention, it is preferable that at least one of R¹′ andR²′ be a hydrogen atom. That is, it is preferable that the aciddissociable, dissolution inhibiting group (p1) is a group represented bygeneral formula (p1-1) shown below.

wherein R¹′, n and Y are respectively as defined for R¹′, n and Y ingeneral formula (p1) above.

As the lower alkyl group for Y, the same as the lower alkyl groups for Rabove can be mentioned.

As the aliphatic cyclic group for Y, any of the aliphaticmonocyclic/polycyclic groups which have been proposed for conventionalArF resists and the like can be appropriately selected for use. Forexample, the same groups described above in connection with the“aliphatic cyclic group” can be mentioned.

Further, as the acetal-type, acid dissociable, dissolution inhibitinggroup, groups represented by general formula (p2) shown below can alsobe exemplified.

wherein R¹⁷ and R¹⁸ each independently represents a linear or branchedalkyl group or a hydrogen atom; and R¹⁹ represents a linear, branched orcyclic alkyl group; or R¹⁷ and R¹⁹ each independently represents alinear or branched alkylene group, wherein the terminal of R¹⁷ may bebonded to the terminal of R¹⁹ to form a ring.

The alkyl group for R¹⁷ and R¹⁸ preferably has 1 to 15 carbon atoms, andmay be either linear or branched. As the alkyl group, an ethyl group ora methyl group is preferable, and a methyl group is most preferable.

It is particularly desirable that either one of R¹⁷ and R¹⁸ be ahydrogen atom, and the other be a methyl group.

R¹⁹ represents a linear, branched or cyclic alkyl group which preferablyhas 1 to 15 carbon atoms, and may be any of linear, branched or cyclic.

When R¹⁹ represents a linear or branched alkyl group, it is preferablyan alkyl group of 1 to 5 carbon atoms, more preferably an ethyl group ora methyl group, and most preferably an ethyl group.

When R¹⁹ represents a cycloalkyl group, it preferably has 4 to 15 carbonatoms, more preferably 4 to 12 carbon atoms, and most preferably 5 to 10carbon atoms. As examples of the cycloalkyl group, groups in which oneor more hydrogen atoms have been removed from a monocycloalkane or apolycycloalkane such as a bicycloalkane, tricycloalkane ortetracycloalkane, which may or may not be substituted with a fluorineatom or a fluorinated alkyl group, may be exemplified. Specific examplesinclude groups in which one or more hydrogen atoms have been removedfrom a monocycloalkane such as cyclopentane or cyclohexane, and groupsin which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane. Of these, a group in which one ormore hydrogen atoms have been removed from adamantane is preferable.

In general formula (p2) above, R¹⁷ and R¹⁹ may each independentlyrepresent a linear or branched alkylene group preferably an alkylenegroup of 1 to 5 carbon atoms), and the terminal of R¹⁹ may be bonded tothe terminal of R¹⁷

In such a case, a cyclic group is formed by R¹⁷, R¹⁹, the oxygen atomhaving R¹⁹ bonded thereto and the carbon atom having the oxygen atom andR¹⁷ bonded thereto. Such a cyclic group is preferably a 4 to 7-memberedring, and more preferably a 4 to 6-membered ring. Specific examples ofthe cyclic group include a tetrahydropyranyl group and atetrahydrofuranyl group.

As the structural unit (a1), it is preferable to use at least one memberselected from the group consisting of structural units represented byformula (a0-1) shown below and structural units represented by formula(a0-2) shown below.

wherein R represents a hydrogen atom, a halogen atom, a lower alkylgroup or a halogenated lower alkyl group; and X¹ represents an aciddissociable, dissolution inhibiting group.

wherein R represents a hydrogen atom, a halogen atom, a lower alkylgroup or a halogenated lower alkyl group; X² represents an aciddissociable, dissolution inhibiting group; and Y² represents an alkylenegroup or an aliphatic cyclic group.

In general formula (a0-1) shown above, as the halogen atom, lower alkylgroup and halogenated lower alkyl group for R, the same as the halogenatom, lower alkyl group and halogenated lower alkyl group for R ingeneral formula (a0-1) above can be mentioned.

X¹ is not particularly limited as long as it is an acid dissociable,dissolution inhibiting group. Examples thereof include theaforementioned tertiary alkyl ester-type acid dissociable, dissolutioninhibiting groups and acetal-type acid dissociable, dissolutioninhibiting groups, and tertiary alkyl ester-type acid dissociable,dissolution inhibiting groups are preferable.

In general formula (a1-0-2), R is as defined for R in general formula(a1-0-1) above.

X² is the same as X¹ in general formula (a1-0-1).

Y² represents an alkylene group or an aliphatic cyclic group, and ispreferably an alkylene group of 1 to 4 carbon atoms or a divalentaliphatic cyclic group. As the aliphatic cyclic group, the same as thoseexemplified above in connection with the explanation of “aliphaticcyclic group” can be used, except that two or more hydrogen atoms havebeen removed therefrom.

Specific examples of the structural unit (a1) include structural unitsrepresented by general formulas (a1-1) to (a1-4) shown below.

wherein X′ represents a tertiary alkyl ester-type acid dissociable,dissolution inhibiting group; Y represents a lower alkyl group of 1 to 5carbon atoms or an aliphatic cyclic group; n represents an integer of 0to 3; m represents 0 or 1; R represents a hydrogen atom, a halogen atom,a lower alkyl group or a halogenated lower alkyl group; and each of R¹′and R²′ independently represents a hydrogen atom or a lower alkyl groupof 1 to 5 carbon atoms.

In general formulas (a1-1) to (a1-4), the halogen atom, lower alkylgroup and halogenated lower alkyl group for R are the same as thehalogen atom, lower alkyl group and halogenated lower alkyl group whichcan be bonded to the α-position of the aforementioned acrylate ester.

It is preferable that at least one of R¹′ and R²′ represent a hydrogenatom, and it is more preferable that both of R¹′ and R²′ represent ahydrogen atom. n is preferably 0 or 1.

Examples of the tertiary alkyl ester-type acid dissociable, dissolutioninhibiting group for X′ are the same as the above-exemplified tertiaryalkyl ester-type acid dissociable, dissolution inhibiting groups for X¹.

Examples of the aliphatic cyclic group for Y are the same as thoseexemplified above in connection with the explanation of “aliphaticcyclic group” in structural unit (a0-1).

Specific examples of structural units represented by general formulas(a1-1) to (a1-4) above are shown below.

Among these, structural units represented by general formula (a1-1) arepreferable. More specifically, at least one structural unit selectedfrom the group consisting of structural units represented by formulas(a1-1-1) to (a-1-1-6) and (a1-1-35) to (a1-1-41) is more preferable.

Further, as the structural unit (a1), structural units represented bygeneral formula (a1-1-01) shown below which includes the structuralunits represented by formulas (a1-1-1) to (a1-1-4), and structural unitsrepresented by general formula (a1-1-02) shown below which includes thestructural units represented by formulas (a1-1-35) to (a1-1-41) are alsopreferable.

wherein R represents a hydrogen atom, a halogen atom, a lower alkylgroup or a halogenated lower alkyl group; and R¹¹ represents a loweralkyl group.

wherein R represents a hydrogen atom, a halogen atom, a lower alkylgroup or a halogenated lower alkyl group; R¹² represents a lower alkylgroup; and h represents an integer of 1 to 3.

In general formula (a1-1-01), R is as defined for R in general formula(a0-1) above. The lower alkyl group for R¹¹ is the same as the loweralkyl group for R above, and is preferably a methyl group or an ethylgroup.

In general formula (a1-1-02), R is as defined for R in general formula(a0-1) above. The lower alkyl group for R¹² is the same as the loweralkyl group for R above. R¹² is preferably a methyl group or an ethylgroup, and most preferably an ethyl group. h is preferably 1 or 2, andmost preferably 2.

As the structural unit (a1), one type of structural unit may be usedalone, or two or more types of structural units may be used incombination.

In the component (A), the amount of the structural unit (a1) based onthe combined total of all structural units constituting the component(A) is preferably 10 to 80 mol %, more preferably 20 to 70 mol %, andstill more preferably 25 to 50 mol %. By making the amount of thestructural unit (a1) at least as large as 10 mol %, a pattern can beeasily formed using a resist composition prepared from the component(A). On the other hand, by making the amount of the structural unit (a1)no more than 80 mol %, a good balance can be achieved with the otherstructural units.

When the structural unit (a0-1) has an acid dissociable, dissolutioninhibiting group, the structural unit (a0-1) may be regarded as astructural unit (a1). However, in the present invention, such astructural unit is included in the structural unit (a0-1), but notincluded in the structural unit (a1). That is, the structural unitrepresented by general formula (a0-1) above is not included in thestructural unit (a1).

[Structural Unit (a2)]

The component (A) preferably has a structural unit (a2) derived from anacrylate ester having a lactone-containing cyclic group, as well as thestructural unit (a0-1) and the structural unit (a0-2), or the structuralunit (a0-1), the structural unit (a0-2) and the structural unit (a1).

The term “lactone-containing cyclic group” refers to a cyclic groupincluding one ring containing a —O—C(O)— structure (lactone ring). Theterm “lactone ring” refers to a single ring containing a —O—C(O)—structure, and this ring is counted as the first ring. Alactone-containing cyclic group in which the only ring structure is thelactone ring is referred to as a monocyclic group, and groups containingother ring structures are described as polycyclic groups regardless ofthe structure of the other rings.

When the component (A) is used for forming a resist film, thelactone-containing cyclic group of the structural unit (a2) is effectivein improving the adhesion between the resist film and the substrate, andincreasing the hydrophilicity with the developing solution.

As the structural unit (a2), there is no particular limitation, and anarbitrary structural unit may be used.

Specific examples of lactone-containing monocyclic groups include groupsin which one hydrogen atom has been removed from γ-butyrolactone.Further, specific examples of lactone-containing polycyclic groupsinclude groups in which one hydrogen atom has been removed from alactone ring-containing bicycloalkane, tricycloalkane ortetracycloalkane.

More specifically, examples of the structural unit (a2) includestructural units represented by general formulas (a2-1) to (a2-5) shownbelow.

wherein R represents a hydrogen atom, a halogen atom, a lower alkylgroup or a halogenated lower alkyl group; R′ represents a hydrogen atom,a lower alkyl group or an alkoxy group of 1 to 5 carbon atoms; and mrepresents an integer of 0 or 1.

In general formulas (a2-1) to (a2-5), R is the same as R in generalformula (a0-1) for the structural unit (a1) above.

The lower alkyl group for R′ is the same as the lower alkyl group for Rin general formula (a1-0-1) for the structural unit (a1) above.

In the structural units represented by general formulas (a2-1) to(a2-5), in consideration of industrial availability, R′ is preferably ahydrogen atom.

Specific examples of structural units represented by general formulas(a2-1) to (a2-5) above are shown below.

In the structural units represented by general formulas (a2-1) to(a2-5), in consideration of industrial availability, R′ is preferably ahydrogen atom.

Of these, at least one structural unit selected from the groupconsisting of structural units represented by general formulas (a2-1),(a2-2) and (a2-3) is preferable. Specifically, it is preferable to useat least one structural unit selected from the group consisting offormulas (a2-1-1), (a2-1-2), (a2-2-1), (a2-2-2), (a2-3-1), (a2-3-2),(a2-3-9) and (a2-3-10).

In the component (A), as the structural unit (a2), one type ofstructural unit may be used, or two or more types of structural unitsmay be used in combination.

In the component (A), the amount of the structural unit (a2) based onthe combined total of all structural units constituting the component(A) is preferably 5 to 60 mol %, more preferably 1 to 50 mol %, andstill more preferably 20 to 50 mol %. By making the amount of thestructural unit (a2) at least as large as 5 mol %, the effect of usingthe structural unit (a2) can be satisfactorily achieved. On the otherhand, by making the amount of the structural unit (a2) no more than 60mol %, a good balance can be achieved with the other structural units.

[Other Structural Units]

The component (A) may also have structural units which are other thanthe aforementioned structural units (a0-1), (a0-2), (a1) and (a2), aslong as the effects of the present invention are not impaired. As thestructural unit which is other than the above-mentioned structural units(a0-1), (a0-2),(a1) and (a2), any other structural unit which cannot beclassified as one of the above structural units (a0-1), (a0-2),(a1) and(a2) can be used without any particular restrictions, and any of themultitude of conventional structural units used within resist resins forArF excimer lasers or KrF excimer lasers (and particularly for ArFexcimer lasers) can be used, as long as the effects of the presentinvention are not impaired.

As such structural units, structural units (a3) and (a4) shown below canbe exemplified.

[Structural Unit (a3)]

The structural unit (a3) is a structural unit derived from an acrylateester containing a polar group-containing aliphatic hydrocarbon group,and is not included in the aforementioned structural unit (a0-1) or(a0-2). The structural unit (a3) enhances the hydrophilicity of thecomponent (A), and improves the compatibility of the component (A) withthe developing solution. As a result, the alkali solubility of theexposed portions improves, which contributes to favorable improvementsin the resolution.

Examples of the polar group include a hydroxyl group, a cyano group, acarboxyl group, or a hydroxyalkyl group in which a part of the hydrogenatoms of the alkyl group have been substituted with fluorine atoms(i.e., fluorinated alkylalcohol).

Examples of the aliphatic hydrocarbon group include linear or branchedhydrocarbon groups (and preferably alkylene groups) of 1 to 10 carbonatoms, and polycyclic aliphatic hydrocarbon groups (polycyclic groups).These polycyclic groups can be selected appropriately from the multitudeof groups that have been proposed for the resins of resist compositionsdesigned for use with ArF excimer lasers. The polycyclic grouppreferably has 7 to 30 carbon atoms.

Of the various possibilities, structural units derived from an acrylateester that include an aliphatic polycyclic group (an aliphatic cyclicgroup which is polycyclic) that contains a hydroxyl group, a cyanogroup, a carboxyl group or a hydroxyalkyl group in which a part of thehydrogen atoms of the alkyl group have been substituted with fluorineatoms are particularly desirable. Examples of the polycyclic groupsinclude groups in which one or more hydrogen atoms have been removedfrom a bicycloalkane, tricycloalkane, tetracycloalkane or the like.Specific examples include groups in which one or more hydrogen atomshave been removed from a polycycloalkane such as adamantane, norbornane,isobornane, tricyclodecane or tetracyclododecane. Of these polycyclicgroups, groups in which two or more hydrogen atoms have been removedfrom adamantane, norbornane or tetracyclododecane are preferredindustrially.

When the aliphatic hydrocarbon group within the polar group-containingaliphatic hydrocarbon group is a linear or branched hydrocarbon group of1 to 10 carbon atoms, the structural unit (a3) is preferably astructural unit derived from a hydroxyethyl ester of acrylic acid. Onthe other hand, when the hydrocarbon group is a polycyclic group,structural units represented by general formulas (a3-1) and (a3-2) shownbelow, and the like are preferable.

wherein R represents a hydrogen atom, a halogen atom, a lower alkylgroup or a halogenated lower alkyl group; k is an integer of 1 to 3; t′is an integer of 1 to 3; 1 is an integer of 1 to 5; and s is an integerof 1 to 3.

In general formulas (a3-1) and (a3-2), the halogen atom, lower alkylgroup and halogenated lower alkyl group for R are the same as thehalogen atom, lower alkyl group and halogenated lower alkyl group whichcan be bonded to the α-position of the aforementioned acrylate ester.

In formula (a3-1), k is preferably 1. The cyano group is preferablybonded to the 5th or 6th position of the norbonyl group.

In formula (a3-2), t′ is preferably 1, 1 is preferably 1 and s ispreferably 1. Further, it is preferable that a 2-norbonyl group or3-norbonyl group be bonded to the terminal of the carboxy group of theacrylic acid. The fluorinated alkylalcohol (hydroxyalkyl group in whicha part of the hydrogen atoms of the alkyl group has been substitutedwith fluorine atoms) is preferably bonded to the 5th or 6th position ofthe norbonyl group. When the structural unit (a3) is included in thecomponent (A), the amount of the structural unit (a3) based on thecombined total of all structural units constituting the component (A) ispreferably 1 to 30 mol %, more preferably 5 to 30 mol %, still morepreferably 10 to 20 mol %.

[Structural Unit (a4)]

The structural unit (a4) is a structural unit derived from an acrylateester containing a non-acid dissociable, aliphatic cyclic group.

Examples of the polycyclic group with the structural unit (a4) includethe same groups as those described above in connection with theaforementioned structural unit (a1), and any of the multitude ofconventional polycyclic groups used within the resin component of resistcompositions for ArF excimer lasers or KrF excimer lasers (andparticularly for ArF excimer lasers) can be used.

In consideration of industrial availability and the like, at least onepolycyclic group selected from among a tricyclodecanyl group, adamantylgroup, tetracyclododecanyl group, isobornyl group, and norbormyl groupis particularly desirable. These polycyclic groups may or may not have asubstituent. As the substituent, a linear or branched alkyl group of 1to 5 carbon atoms can be mentioned.

Specific examples of the structural unit (a4) include units withstructures represented by general formulas (a-1) to (a-4-5) shown below.

wherein R represents a hydrogen atom, a halogen atom, a lower alkylgroup or a halogenated lower alkyl group.

In general formulas (a4-1) to (a4-5), the halogen atom, lower alkylgroup and halogenated lower alkyl group for R are the same as thehalogen atom, lower alkyl group and halogenated lower alkyl group whichcan be bonded to the α-position of the aforementioned acrylate ester.

When the structural unit (a4) is included in the component (A), theamount of the structural unit (a4) based on the combined total of allstructural units constituting the component (A) is preferably 1 to 30mol %, more preferably 10 to 20 mol %. In the present invention, thecomponent (A) includes at least the structural unit (a0-1) and thestructural unit (a0-2).

In the present invention, the component (A) preferably contains acopolymer which has the aforementioned structural unit (a0-1) andstructural unit (a0-2), and if desired, at least one of the structuralunits (a1), (a2), (a3) and (a4).

In the present invention, the component (A) preferably contains acopolymer which has at least the three structural units (a0-1), (a0-2)and (a1). Examples of such copolymers include a tertiary copolymerconsisting of the aforementioned structural units (a0-1), (a0-2) and(a1), and a quaternary copolymer consisting of the aforementionedstructural units (a0-1), (a0-2), (a1) and (a2).

In the present invention, it is particularly desirable that thecomponent (A) contain at least one copolymer selected from the groupconsisting of a copolymer (A-11) which includes the combination of 4structural units represented by general formula (A-11) shown below; acopolymer (A-12) which includes the combination of 4 structural unitsrepresented by general formula (A-12) shown below; and a copolymer(A-13) which includes the combination of 4 structural units representedby general formula (A-13) shown below. Among these, it is particularlydesirable that the component (A) contain a copolymer (A-11) and/or acopolymer (A-12), and a copolymer (A-13).

wherein:in general formula (A-11), R and e are respectively as defined for R ande in general formula (a0-1) above, wherein the plurality of R may be thesame or different; R²¹ to R²³ are respectively as defined for R²¹ to R²³in general formula (I) above; and R²⁷ represents a lower alkyl group;in general formula (A-12), R and e are respectively as defined for R ande in general formula (a0-1) above, wherein the plurality of R may be thesame or different; R²¹ to R²³ are respectively as defined for R²¹ to R²³in general formula (I) above; and R²⁸ represents a lower alkyl group;andin general formula (A-13), R and e are respectively as defined for R ande in general formula (a0-1) above, wherein the plurality of R may be thesame or different; R²¹ to R²³ are respectively as defined for R²¹ to R²³in general formula (I) above; and n is as defined for n in generalformula (p1) above.

In general formula (A-11), as the lower alkyl group for R²⁷, the same asthe lower alkyl group for R can be exemplified. As R²⁷, a methyl groupor an ethyl group is preferable, and a methyl group is particularlydesirable.

In general formula (A-12), as the lower alkyl group for R²⁸, the same asthe lower alkyl group for R can be exemplified. As R²⁸, a methyl groupor an ethyl group is preferable, and a methyl group is particularlydesirable.

In general formula (A-13), n is preferably 0 or 1, and most preferably0.

As the component (A), one type of resin may be used alone, or two ormore types of resins may be used in combination.

The component (A), as described above, may contain one or morecopolymers having both of the structural unit (a0-1) and the structuralunit (a0-2). Alternatively, the component (A) may be a mixture of apolymer having at least the structural unit (a0-1) and a polymer havingat least the structural unit (a0-2).

As the latter mixture, for example, a mixture of the aforementionedcopolymer having both of the structural unit (a0-1) and the structuralunit (a0-2) and a below-mentioned polymer (A2-1) and/or polymer (A2-2);and a mixture of the below-mentioned polymer (A2-1) and polymer (A2-2),can be exemplified.

Polymer (A2-1): a polymer having the structural unit (a0-2) and nostructural unit (a0-1)

Polymer (A2-2): a polymer having the structural unit (a0-1) and nostructural unit (a0-2)

As the polymer (A2-1), for example, a copolymer of the structural unit(a0-2) and at least one of the structural units (a1) to (a4) can beexemplified. Specific examples include a copolymer consisting of thestructural units (a0-2) and (a1), and a copolymer consisting of thestructural units (a0-2), (a1) and (a2). As such copolymers, copolymersconsisting of three structural units represented by general formulas(A-11), (A-12) and (A-13) above excluding the structural unitcorresponding to the structural unit (a0-1), can be mentioned.

As the polymer (A2-2), for example, a copolymer of the structural unit(a0-1) and at least one of the structural units (a1) to (a4) can beexemplified. Specific examples include a copolymer consisting of thestructural units (a0-1) and (a1), and a copolymer consisting of thestructural units (a0-1), (a1) and (a2). As such copolymers, copolymersconsisting of three structural units represented by general formulas(A-11), (A-12) and (A-13) above excluding the structural unitcorresponding to the structural unit (a0-2); and a copolymer representedby general formula (A2-21) shown below, can be exemplified.

In general formula (A2-21), R and e are respectively as defined for Rand e in general formula (a0-1) above, wherein the plurality of R maythe same or different; R²¹ to R²³ are respectively as defined for R²¹ toR²³ in general formula (I) above; and R³⁰ represents a lower alkylgroup.

In general formula (A2-21), as the lower alkyl group for R³⁰, the sameas the lower alkyl group for R can be exemplified. As R³⁰, a methylgroup or an ethyl group is preferable, and a methyl group isparticularly desirable.

The component (A) can be obtained, for example, by a conventionalradical polymerization or the like of the monomers corresponding witheach of the structural units, using a radical polymerization initiatorsuch as azobisisobutyronitrile (AIBN).

Furthermore, in the component (A), by using a chain transfer agent suchas HS—CH₂—CH₂—CH₂—C(CF₃)₂—OH, a —C(CF₃)₂—OH group can be introduced atthe terminals of the component (A). Such a copolymer having introduced ahydroxyalkyl group in which a part of the hydrogen atoms of the alkylgroup are substituted with fluorine atoms is effective in reducing LWR(line width roughness). Such a copolymer is also effective in reducingdeveloping defects and LER (line edge roughness: unevenness of the sidewalls of a line pattern).

The weight average molecular weight (Mw) (the polystyrene equivalentvalue determined by gel permeation chromatography) of the component (A)is not particularly limited, but is preferably 2,000 to 50,000, morepreferably 3,000 to 30,000, and most preferably 5,000 to 20,000. Bymaking the weight average molecular weight no more than the upper limitof the above-mentioned range, the component (A) exhibits satisfactorysolubility in a resist solvent when used as a resist. On the other hand,by making the weight average molecular weight at least as large as thelower limit of the above-mentioned range, dry etching resistance andcross-sectional shape of the resist pattern becomes satisfactory.

Further, the dispersity (Mw/number average molecular weight (Mn)) ispreferably 1.0 to 5.0, more preferably 1.0 to 3.0, and most preferably1.2 to 2.5. Here, Mn is the number average molecular weight.

<Component (B)>

As the component (B), there is no particular limitation, and any of theknown acid generators used in conventional chemically amplified resistcompositions can be used.

Examples of these acid generators are numerous, and include oniumsalt-based acid generators such as iodonium salts and sulfonium salts;oxime sulfonate-based acid generators; diazomethane-based acidgenerators such as bisalkyl or bisaryl sulfonyl diazomethanes andpoly(bis-sulfonyl)diazomethanes; nitrobenzylsulfonate-based acidgenerators; iminosulfonate-based acid generators; and disulfone-basedacid generators.

As an onium salt-based acid generator, for example, a compoundrepresented by general formula (b-0) shown below can be used.

wherein R⁵⁴ represents a linear, branched or cyclic alkyl group, or alinear, branched or cyclic fluorinated alkyl group; R⁵² represents ahydrogen atom, a hydroxyl group, a halogen atom, a linear or branchedalkyl group, a linear or branched halogenated alkyl group, or a linearor branched alkoxy group; R⁵³ represents an aryl group which may have asubstituent; and u″ represents an integer of 1 to 3.

In general formula (b-0), R⁵¹ represents a linear, branched or cyclicalkyl group, or a linear, branched or cyclic fluorinated alkyl group.

The linear or branched alkyl group preferably has 1 to 10 carbon atoms,more preferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbonatoms.

The cyclic alkyl group preferably has 4 to 12 carbon atoms, morepreferably 5 to 10 carbon atoms, and most preferably 6 to 10 carbonatoms.

The fluorinated alkyl group preferably has 1 to 10 carbon atoms, morepreferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbon atoms.The fluorination ratio of the fluorinated alkyl group (percentage of thenumber of fluorine atoms substituting the hydrogen atoms, based on thetotal number of all hydrogen atoms within the alkyl group) is preferablyfrom 10 to 100%, more preferably from 50 to 100%, and it is particularlydesirable that all of the hydrogen atoms are substituted with fluorineatoms, as the acid strength increases.

R⁵¹ is most preferably a linear alkyl group or a fluorinated alkylgroup.

R⁵² represents a hydrogen atom, a hydroxyl group, a halogen atom, alinear or branched alkyl group, a linear or branched halogenated alkylgroup, or a linear or branched alkoxy group.

Examples of the halogen atom for R include a fluorine atom, a bromineatom, a chlorine atom and an iodine atom, and a fluorine atom ispreferable.

The alkyl group for R⁵² is linear or branched, and preferably has 1 to 5carbon atoms, more preferably 1 to 4 carbon atoms, and most preferably 1to 3 carbon atoms.

The halogenated alkyl group for R⁵² is a group in which some or all ofthe hydrogen atoms of the alkyl group have been substituted with halogenatoms. As the alkyl group of the halogenated alkyl group, the same asthe linear or branched alkyl group for R⁵² may be mentioned. As thehalogen atoms for substituting the hydrogen atoms of the alkyl group,the same as the halogen atom for R⁵² may be mentioned. In thehalogenated alkyl group, it is preferable that 50 to 100% of thehydrogen atoms of the alkyl group be substituted with halogen atoms, andit is more preferable that all of the hydrogen atoms are substitutedwith halogen atoms.

The alkoxy group for R⁵² is linear or branched, and preferably has 1 to5 carbon atoms, more preferably 1 to 4 carbon atoms, and most preferably1 to 3 carbon atoms.

Among these, as R⁵², a hydrogen atom is particularly desirable.

R⁵³ represents an aryl group which may have a substituent, and examplesof the basic ring excluding the substituent include a naphthyl group, aphenyl group and an anthracenyl group. In terms of the effects of thepresent invention and absorption of exposure rays such as ArF excimerlaser, a phenyl group is preferable.

Examples of the substituent include a hydroxyl group and a lower alkylgroup (linear or branched, and preferably has 1 to 5 carbon atoms, and amethyl group is particularly desirable).

As the aryl group for R⁵³, those which do not have a substituent arepreferable.

u″ is an integer of 1 to 3, preferably 2 or 3, and it is particularlydesirable that u″ be 3.

As preferable examples of acid generators represented by general formula(b-0), the following can be mentioned.

As an onium salt-based acid generator other than those represented bygeneral formula (b-0), a compound represented by general formula (b-1)or (b-2) shown below can be mentioned.

wherein R¹″ to R³″, R⁵″ and R⁶″ each independently represents an arylgroup or alkyl group; and R⁴″ represents a linear, branched or cyclicalkyl group or fluorinated alkyl group, with the proviso that at leastone of R¹″ to R³″ represents an aryl group, and at least one of R⁵″ andR⁶″ represents an aryl group.

In formula (b-1), R¹′ to R³″ each independently represents an aryl groupor an alkyl group. Further, among R¹″ to R³″, at least one grouprepresents an aryl group. Among R¹″ to R³″, two or more groups arepreferably aryl groups, and it is particularly desirable that all of R¹″to R³″ are aryl groups.

The aryl group for R¹″ to R³″ is not particularly limited. For example,an aryl group having 6 to 20 carbon atoms may be used in which some orall of the hydrogen atoms of the aryl group may or may not besubstituted with alkyl groups, alkoxy groups, or halogen atoms.

The aryl group is preferably an aryl group having 6 to 10 carbon atomsbecause it can be synthesized at a low cost. Specific examples thereofinclude a phenyl group and naphthyl group.

The alkyl group, with which hydrogen atoms of the aryl group may besubstituted, is preferably an alkyl group having 1 to 5 carbon atoms,and most preferably a methyl group, an ethyl group, a propyl group, ann-butyl group, or a tert-butyl group.

The alkoxy group, with which hydrogen atoms of the aryl group may besubstituted, is preferably an alkoxy group having 1 to 5 carbon atoms,and most preferably a methoxy group or an ethoxy group.

The halogen atom, with which hydrogen atoms of the aryl group may besubstituted, is preferably a fluorine atom.

The alkyl group for R¹″ to R³″ is not particularly limited and includes,for example, a linear, branched or cyclic alkyl group having 1 to 10carbon atoms. In terms of achieving excellent resolution, the alkylgroup preferably has 1 to 5 carbon atoms. Specific examples thereofinclude a methyl group, an ethyl group, an n-propyl group, an isopropylgroup, an n-butyl group, an isobutyl group, an n-pentyl group, acyclopentyl group, a hexyl group, a cyclohexyl group, a nonyl group, anda decanyl group, and a methyl group is most preferable because it isexcellent in resolution and can be synthesized at a low cost.

It is preferable that each of R¹″ to R³″ is a phenyl group or a naphthylgroup, and it is particularly desirable that one of R¹″ to R³″ is aphenyl group, and the other two are naphthyl groups.

R⁴″ represents a linear, branched or cyclic alkyl group or a fluorinatedalkyl group.

The linear or branched alkyl group preferably has 1 to 10 carbon atoms,more preferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbonatoms.

The cyclic alkyl group is preferably a cyclic group, as described forR′″, having 4 to 15 carbon atoms, more preferably 4 to 10 carbon atoms,and most preferably 6 to 10 carbon atoms.

The fluorinated alkyl group preferably has 1 to 10 carbon atoms, morepreferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbon atoms.Further, the fluorination ratio of the fluorinated alkyl group(percentage of fluorine atoms within the alkyl group) is preferably from10 to 100%, more preferably from 50 to 100%, and it is particularlydesirable that all hydrogen atoms are substituted with fluorine atomsbecause the acid strength increases.

R⁴″ is most preferably a linear or cyclic alkyl group or a fluorinatedalkyl group.

In formula (b-2), R⁵″ and R⁶″ each independently represents an arylgroup or an alkyl group. At least one of R⁵″ and R⁶″ represents an arylgroup. It is preferable that both of R⁵″ and R⁶″ represent an arylgroup.

As the aryl group for R⁵″ and R⁶″, the same aryl groups as those for R¹″to R³″ can be mentioned.

As the alkyl group for R⁵″ and R⁶″, the same alkyl groups as those forR¹″ to R³″ can be mentioned.

It is particularly desirable that both of R⁵″ and R⁶″ represents aphenyl group.

As R⁴″ in formula (b-2), the same R⁴″ as those mentioned above for R⁴″in formula (b-1) can be mentioned.

Specific examples of suitable onium salt-based acid generatorsrepresented by formula (b-1) or (b-2) include diphenyliodoniumtrifluoromethanesulfonate or nonafluorobutanesulfonate;bis(4-tert-butylphenyl)iodonium trifluoromethanesulfonate ornonafluorobutanesulfonate; triphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;tri(4-methylphenyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;dimethyl(4-hydroxynaphthyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;monophenyldimethylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;diphenylmonomethylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;(4-methylphenyl)diphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;(4-methoxyphenyl)diphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;tri(4-tert-butyl)phenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;diphenyl(1-(4-methoxy)naphthyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate; anddi(1-naphthyl)phenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate. It is alsopossible to use onium salts in which the anion moiety of these oniumsalts are replaced by methanesulfonate, n-propanesulfonate,n-butanesulfonate, or n-octanesulfonate.

Further, onium salt-based acid generators in which the anion moiety ingeneral formula (b-1) or (b-2) is replaced by an anion moietyrepresented by general formula (b-3) or (b-4) shown below (the cationmoiety is the same cation as (b-1) or (b-2)) may also be used.

wherein X″ represents an alkylene group of 2 to 6 carbon atoms in whichat least one hydrogen atom has been substituted with a fluorine atom;and Y″ and Z″ each independently represents an alkyl group of 1 to 10carbon atoms in which at least one hydrogen atom has been substitutedwith a fluorine atom.

X″ represents a linear or branched alkylene group in which at least onehydrogen atom has been substituted with a fluorine atom, and thealkylene group has 2 to 6 carbon atoms, preferably 3 to 5 carbon atoms,and most preferably 3 carbon atoms.

Y″ and Z″ each independently represents a linear or branched alkyl groupin which at least one hydrogen atom has been substituted with a fluorineatom, and the alkyl group has 1 to 10 carbon atoms, preferably 1 to 7carbon atoms, and more preferably 1 to 3 carbon atoms.

The smaller the number of carbon atoms of the alkylene group for X″ orthose of the alkyl group for Y″ and Z″ within the above-mentioned rangeof the number of carbon atoms, the more preferable since the solubilityin a resist solvent is improved.

Further, in the alkylene group for X″ or the alkyl group for Y″ and Z″,it is preferable that the number of hydrogen atoms substituted withfluorine atoms is as large as possible because the acid strengthincreases and the transparency to high energy radiation of 200 nm orless or electron beam is improved. The percentage of the fluorine atomswithin the alkylene group or alkyl group, i.e., the fluorination ratiois preferably from 70 to 100%, more preferably from 90 to 100%, and itis particularly desirable that the alkylene group or alkyl group be aperfluoroalkylene or perfluoroalkyl group in which all hydrogen atomsare substituted with fluorine atoms.

Furthermore, as an onium salt-based acid generator, a sulfonium salthaving a cation moiety represented by general formula (b-5) or (b-6)shown below may be used.

wherein R⁴¹″ to R⁴⁶″ each independently represents an alkyl group, anacetyl group, an alkoxy group, a carboxy group, a hydroxyl group or ahydroxyalkyl group; n₁ to n₅ each independently represents an integer of0 to 3; and n₆ represents an integer of 0 to 2.

With respect to R⁴¹″ to R⁴⁶″, the alkyl group is preferably a loweralkyl group of 1 to 5 carbon atoms, more preferably a linear or branchedalkyl group, and most preferably a methyl group, an ethyl group, apropyl group, an isopropyl group, an n-butyl group or a tert butylgroup.

The alkoxy group is preferably an alkoxy group of 1 to 5 carbon atoms,more preferably a linear or branched alkoxy group, and most preferably amethoxy group or an ethoxy group.

The hydroxyalkyl group is preferably the aforementioned alkyl group inwhich one or more hydrogen atoms have been substituted with hydroxygroups, and examples thereof include a hydroxymethyl group, ahydroxyethyl group and a hydroxypropyl group.

n₁ is preferably 1 or 2, and more preferably 1.

It is preferable that n₂ and n₃ each independently represent 0 or 1, andmore preferably 0.

n₄ is preferably 1 or 2, and more preferably 1.

n₅ is preferably 0 or 1, and more preferably 0.

n₆ is preferably 0 or 1, and more preferably 1.

The anion moiety of the sulfonium salt having a cation moietyrepresented by general formula (b-5) or (b-6) is not particularlylimited, and the same anion moieties for onium salt-based acidgenerators which have been proposed may be used. Examples of such anionmoieties include anion moieties (R⁵¹—SO₃ ⁻) for onium salt-based acidgenerators represented by general formula (b-0); anion moieties (R⁴″—SO₃⁻ for onium salt-based acid generators represented by general formula(b-1) or (b-2) shown above; and anion moieties represented by generalformula (b-3) or (b-4) shown above.

Specific examples of sulfonium salts having a cation moiety representedby formula (b-5) or (b-6) are shown below.

In the present description, an oximesulfonate-based acid generator is acompound having at least one group represented by general formula (B-1)shown below, and has a feature of generating acid by irradiation. Suchoximesulfonate-based acid generators are widely used for a chemicallyamplified resist composition, and can be appropriately selected.

wherein R³¹ and R³² each independently represents an organic group.

The organic group for R³¹ and R³² refers to a group containing a carbonatom, and may include atoms other than carbon atoms (e.g., a hydrogenatom, an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom(such as a fluorine atom and a chlorine atom) and the like).

As the organic group for R³¹, a linear, branched, or cyclic alkyl groupor aryl group is preferable. The alkyl group or the aryl group may havea substituent. The substituent is not particularly limited, and examplesthereof include a fluorine atom and a linear, branched, or cyclic alkylgroup having 1 to 6 carbon atoms. The expression “having a substituent”means that some or all of the hydrogen atoms of the alkyl group or thearyl group are substituted with substituents.

The alkyl group preferably has 1 to 20 carbon atoms, more preferably 1to 10 carbon atoms, still more preferably 1 to 8 carbon atoms, stillmore preferably 1 to 6 carbon atoms, and most preferably 1 to 4 carbonatoms. As the alkyl group, a partially or completely halogenated alkylgroup (hereinafter, sometimes referred to as a “halogenated alkylgroup”) is particularly desirable. The “partially halogenated alkylgroup” refers to an alkyl group in which some of the hydrogen atoms aresubstituted with halogen atoms, and the “completely halogenated alkylgroup” refers to an alkyl group in which all of the hydrogen atoms aresubstituted with halogen atoms. Examples of the halogen atom include afluorine atom, a chlorine atom, a bromine atom and an iodine atom, and afluorine atom is particularly desirable. In other words, the halogenatedalkyl group is preferably a fluorinated alkyl group.

The aryl group preferably has 4 to 20 carbon atoms, more preferably 4 to10 carbon atoms, and most preferably 6 to 10 carbon atoms. As the arylgroup, partially or completely halogenated aryl group is particularlydesirable. The “partially halogenated aryl group” refers to an arylgroup in which some of the hydrogen atoms are substituted with halogenatoms, and the “completely halogenated aryl group” refers to an arylgroup in which all of hydrogen atoms are substituted with halogen atoms.

As R⁻, an alkyl group of 1 to 4 carbon atoms which has no substituent ora fluorinated alkyl group of 1 to 4 carbon atoms is particularlydesirable.

As the organic group for R³², a linear, branched, or cyclic alkyl group,aryl group, or cyano group is preferable. Examples of the alkyl groupand the aryl group for R³² are the same as those of the alkyl group andthe aryl group for R³¹.

As R³², a cyano group, an alkyl group of 1 to 8 carbon atoms having nosubstituent or a fluorinated alkyl group of 1 to 8 carbon atoms isparticularly desirable.

Preferred examples of the oxime sulfonate-based acid generator includecompounds represented by general formula (B-2) or (B-3) shown below.

wherein R³³ represents a cyano group, an alkyl group having nosubstituent or a halogenated alkyl group; R³⁴ represents an aryl group;and R³⁵ represents an alkyl group having no substituent or a halogenatedalkyl group.

wherein R³⁶ represents a cyano group, an alkyl group having nosubstituent or a halogenated alkyl group; R³⁷ represents a divalent ortrivalent aromatic hydrocarbon group; R³⁸ represents an alkyl grouphaving no substituent or a halogenated alkyl group; and p″ represents 2or 3.

In general formula (B-2), the alkyl group having no substituent or thehalogenated alkyl group for R³³ preferably has 1 to 10 carbon atoms,more preferably 1 to 8 carbon atoms, and most preferably 1 to 6 carbonatoms.

As R³³, a halogenated alkyl group is preferable, and a fluorinated alkylgroup is more preferable.

The fluorinated alkyl group for R³³ preferably has 50% or more of thehydrogen atoms thereof fluorinated, more preferably 70% or more, andstill more preferably 90% or more.

Examples of the aryl group for R³⁴ include groups in which one hydrogenatom has been removed from an aromatic hydrocarbon ring, such as aphenyl group, a biphenyl group, a fluorenyl group, a naphthyl group, ananthracyl group, and a phenanthryl group, and heteroaryl groups in whichsome of the carbon atoms constituting the ring(s) of these groups aresubstituted with hetero atoms such as an oxygen atom, a sulfur atom, anda nitrogen atom. Of these, a fluorenyl group is preferable.

The aryl group for R³⁴ may have a substituent such as an alkyl group of1 to 10 carbon atoms, a halogenated alkyl group, or an alkoxy group. Thealkyl group and halogenated alkyl group as the substituent preferablyhas 1 to 8 carbon atoms, and more preferably 1 to 4 carbon atoms. Thehalogenated alkyl group is preferably a fluorinated alkyl group.

The alkyl group having no substituent or the halogenated alkyl group forR³⁵ preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbonatoms, and most preferably 1 to 6 carbon atoms.

As R³⁵, a halogenated alkyl group is preferable, and a partially orcompletely fluorinated alkyl group is more preferable.

In terms of enhancing the strength of the acid generated, thefluorinated alkyl group for R³⁵ preferably has 50% or more of thehydrogen atoms fluorinated, more preferably 70% or more, still morepreferably 90% or more. A completely fluorinated alkyl group in which100% of the hydrogen atoms are substituted with fluorine atoms isparticularly desirable.

In general formula (B-3), the alkyl group having no substituent and thehalogenated alkyl group for R³⁶ are the same as the alkyl group havingno substituent and the halogenated alkyl group for R³³.

Examples of the divalent or trivalent aromatic hydrocarbon group for R³⁷include groups in which one or two hydrogen atoms have been removed fromthe aryl group for R³⁴.

As the alkyl group having no substituent or the halogenated alkyl groupfor R³⁸, the same one as the alkyl group having no substituent or thehalogenated alkyl group for R³⁵ can be used.

p″ is preferably 2.

Specific examples of suitable oxime sulfonate-based acid generatorsinclude α-(p-toluenesulfonyloxyimino)-benzyl cyanide,α-(p-chlorobenzenesulfonyloxyimino)-benzyl cyanide,α-(4-nitrobenzenesulfonyloxyimino)-benzyl cyanide,α-(4-nitro-2-trifluoromethylbenzenesulfonyloxyimino)-benzyl cyanide,α-(benzenesulfonyloxyimino)-4-chlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-2,4-dichlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-2,6-dichlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-4-methoxybenzyl cyanide,α-(2-chlorobenzenesulifonyloxyimino)-4-methoxybenzyl cyanide,α-(benzenesulfonyloxyimino)-thien-2-yl acetonitrile,α-(4-dodecylbenzenesulfonyloxyimino)benzyl cyanide,α-[(p-toluenesulfonyloxyinino)-4-methoxyphenyl]acetonitrile,α-[(dodecylbenzenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-(tosyloxyimino)-4-thienyl cyanide,α-(methylsulfonytoxyimino)-1-cyclopentenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cycloheptenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cyclooctenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-cyclohexyl acetonitrile,α-(ethylsulfonyloxyimino)-ethyl acetonitrile,α-(propylsulfonyloxyimino)-propyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-cyclopentyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-cyclohexyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(ethylsolfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(n-butylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(ethylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(n-butylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(methylsulfonyloxyimino)-phenyl acetonitrile,α-(methylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-phenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(ethylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(propylsulfonyloxyimino)-p-methylphenyl acetonitrile, andα-(methylsulfonyloxyimino)-p-bromophenyl acetonitrile.

Further, oxime sulfonate-based acid generators disclosed in JapaneseUnexamined Patent Application, First Publication No. Hei 9-208554(Chemical Formulas 18 and 19 shown in paragraphs [0012] to [0014]) andoxime sulfonate-based acid generators disclosed in WO 2004/074242A2(Examples 1 to 40 described at pages 65 to 85) may be preferably used.

Furthermore, as preferable examples, the following can be exemplified.

Further, as more preferable examples of oxime sulfonate-based acidgenerators, the following 4 compounds can be exemplified.

Of the aforementioned diazomethane-based acid generators, specificexamples of suitable bisalkyl or bisaryl sulfonyl diazomethanes includebis(isopropylsulfonyl)diazomethane, bis(p-toluenesulfonyl)diazomethane,bis(1,1-dimethylethylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane, andbis(2,4-dimethylphenylsulfonyl)diazomethane.

Further, diazomethane-based acid generators disclosed in JapaneseUnexamined Patent Application, First Publication No. Hei 11-035551,Japanese Unexamined Patent Application, First Publication No. Hei11-035552 and Japanese Unexamined Patent Application, First PublicationNo. Hei 11-035573 may be preferably used.

Furthermore, as poly(bis-sulfonyl)diazomethanes, those disclosed inJapanese Unexamined Patent Application, First Publication No. Hei11-322707, including 1,3-bis(phenylsulfonyldiazomethylsulfonyl)propane,1,4-bis(phenylsulfonyldiazomethylsulfonyl)butane,1,6-bis(phenylsulfonyldiazomethylsulfonyl)hexane,1,10-bis(phenylsulfonyldiazomethylsulfonyl)decane,1,2-bis(cyclohexylsulfonyldiazomethylsulfonyl)ethane,1,3-bis(cyclohexylsulfonyldiazomethylsulfonyl)propane,1,6-bis(cyclohexylsulfonyldiazomethylsulfonyl)hexane, and1,10-bis(cyclohexylsulfonyldiazomethylsulfonyl)decane, may beexemplified.

As the component (B), one type of these acid generators may be usedalone, or two or more types may be used in combination.

In the present invention, as the component (B), it is particularlypreferable to use an onium salt in which an anion is a fluorinatedalkylsulfonate ion.

The amount of the component (B) within the positive resist compositionof the present invention is preferably 0.5 to 30 parts by weight, morepreferably 1 to 20 parts by weight, and most preferably 2 to 15 parts byweight, relative to 100 parts by weight of the component (A). When theamount of the component (B) is within the above-mentioned range,formation of a resist pattern can be satisfactorily performed. Further,by virtue of the above-mentioned range, a uniform solution can beobtained and the storage stability becomes satisfactory.

<Optional Component>

In the positive resist composition of the present invention, forimproving the resist pattern shape and the post exposure stability ofthe latent image formed by the pattern-wise exposure of the resistlayer, a nitrogen-containing organic compound (D) (hereafter referred toas the component (D)) may be added as an optional component.

A multitude of these components (D) have already been proposed, and anyof these known compounds may be used, although a cyclic amine, analiphatic amine, and particularly a secondary aliphatic amine ortertiary aliphatic amine is preferable. Here, an aliphatic amine is anamine having one or more aliphatic groups, and the aliphatic groupspreferably have 1 to 12 carbon atoms.

Examples of these aliphatic amines include amines in which at least onehydrogen atom of ammonia (NH₃) has been substituted with an alkyl groupor hydroxyalkyl group of 1 to 12 carbon atoms (i.e., alkylamines oralkyl alcohol amines), and cyclic amines.

Specific examples of alkylamines and alkylalcoholamines includemonoalkylamines such as n-hexylamine, n-heptylamine, n-octylamine,n-nonylamine, and n-decylamine; dialkylamines such as diethylamine,di-n-propylamine, di-n-heptylamine, di-n-octylamine, anddicyclohexylamine; trialkylamines such as trimethylamine, triethylamine,tri-n-propylamine, tri-n-butylamine, tri-n-hexylamine,tri-n-pentylamine, tri-n-heptylamine, tri-n-octylamine,tri-n-nonylamine, tri-n-decanylamine, and tri-n-dodecylamine; and alkylalcohol amines such as diethanolamine, triethanolamine,diisopropanolamine, triisopropanolamine, di-n-octanolamine, andtri-n-octanolamine. Among these, trialkylamines of 5 to 10 carbon atomsare preferable, and tri-n-pentylamine is particularly desirable.

Examples of the cyclic amine include heterocyclic compounds containing anitrogen atom as a hetero atom. The heterocyclic compound may be amonocyclic compound (aliphatic monocyclic amine), or a polycycliccompound (aliphatic polycyclic amine).

Specific examples of the aliphatic monocyclic amine include piperidine,and piperazine.

The aliphatic polycyclic amine preferably has 6 to 10 carbon atoms, andspecific examples thereof include 1,5-diazabicyclo[4.3.0]-5-nonene,1,8-diazabicyclo[5.4.0]-7-undecene, hexamethylenetetramine, and1,4-diazabicyclo[2.2.2]octane.

These compounds can be used either alone, or in combinations of two ormore different compounds.

The component (D) is typically used in an amount within a range from0.01 to 5.0 parts by weight, relative to 100 parts by weight of thecomponent (A).

Furthermore, in the positive resist composition of the presentinvention, for preventing any deterioration in sensitivity, andimproving the resist pattern shape and the post exposure stability ofthe latent image formed by the pattern-wise exposure of the resistlayer, at least one compound (E) (hereafter referred to as the component(E)) selected from the group consisting of an organic carboxylic acid,or a phosphorus oxo acid or derivative thereof can be added as anoptional component.

Examples of suitable organic carboxylic acids include acetic acid,malonic acid, citric acid, malic acid, succinic acid, benzoic acid, andsalicylic acid. Among these, salicylic acid is particularly preferable.

Examples of phosphorus oxo acids or derivatives thereof includephosphoric acid, phosphonic acid and phosphinic acid. Among these,phosphonic acid is particularly desirable.

Examples of phosphorus oxo acid derivatives include esters in which ahydrogen atom within the above-mentioned oxo acids is substituted with ahydrocarbon group. Examples of the hydrocarbon group include an alkylgroup of 1 to 5 carbon atoms and an aryl group of 6 to 15 carbon atoms.

Examples of phosphoric acid derivatives include phosphoric acid esterssuch as di-n-butyl phosphate and diphenyl phosphate.

Examples of phosphonic acid derivatives include phosphonic acid esterssuch as dimethyl phosphonate, di-n-butyl phosphonate, phenylphosphonicacid, diphenyl phosphonate and dibenzyl phosphonate.

Examples of phosphinic acid derivatives include phosphinic acid esterssuch as phenylphosphinic acid.

Of these, one type may be used alone, or two or more types may be usedin combination.

As the component (E), an organic carboxylic acid is preferable, andsalicylic acid is particularly desirable.

The component (E) is typically used in an amount within a range from0.01 to 5.0 parts by weight, relative to 100 parts by weight of thecomponent (A).

If desired, other miscible additives can also be added to the positiveresist composition of the present invention. Examples of such miscibleadditives include additive resins for improving the performance of theresist film, surfactants for improving the applicability, dissolutioninhibitors, plasticizers, stabilizers, colorants, halation preventionagents, and dyes.

The positive resist composition of the present invention can be preparedby dissolving the materials for the resist composition (the component(A), component (B), and if desired, the aforementioned optionalcomponents) in an organic solvent (hereafter, frequently referred to as“component (S)”).

The component (S) may be any organic solvent which can dissolve therespective components to give a uniform solution, and any one or morekinds of organic solvents can be appropriately selected from those whichhave been conventionally known as solvents for a chemically amplifiedresist.

Examples thereof include lactones such as γ-butyrolactone; ketones suchas acetone, methyl ethyl ketone, cyclohexanone, methyl-n-amyl ketone,methyl isoamyl ketone, and 2-heptanone; polyhydric alcohols, such asethylene glycol, diethylene glycol, propylene glycol and dipropyleneglycol; compounds having an ester bond, such as ethylene glycolmonoacetate, diethylene glycol monoacetate, propylene glycolmonoacetate, and dipropylene glycol monoacetate; polyhydric alcoholderivatives including compounds having an ether bond, such as amonoalkylether (e.g., monomethylether, monoethylether, monopropyletheror monobutylether) or monophenylether of any of these polyhydricalcohols or compounds having an ester bond (among these, propyleneglycol monomethyl ether acetate (PGMEA) and propylene glycol monomethylether (PGME) are preferable); cyclic ethers such as dioxane; esters suchas methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate,butyl acetate, methyl pyruvate, ethyl pyruvate, methylmethoxypropionate, and ethyl ethoxypropionate; and aromatic organicsolvents such as anisole, ethylbenzylether, cresylmethylether,diphenylether, dibenzylether, phenetole, butylphenylether, ethylbenzene,diethylbenzene, amylbenzene, isopropylbenzene, toluene, xylene, cymeneand mesitylene.

These solvents can be used individually, or in combination as a mixedsolvent.

Among these, propylene glycol monomethyl ether acetate (PGMEA),propylene glycol monomethyl ether (PGME) and ethyl lactate (EL) arepreferable.

Further, among the mixed solvents, a mixed solvent obtained by mixingPGMEA with a polar solvent is preferable. The mixing ratio (weightratio) of the mixed solvent can be appropriately determined, taking intoconsideration the compatibility of the PGMEA with the polar solvent, butis preferably in the range of 1:9 to 9:1, more preferably from 2:8 to8:2.

Specifically, when EL is mixed as the polar solvent, the PGMEA:EL weightratio is preferably from 1:9 to 9:1, and more preferably from 2:8 to8:2. Alternatively, when PGME is mixed as the polar solvent, thePGMEA:PGME weight ratio is preferably from 1:9 to 9:1, more preferablyfrom 2:8 to 8:2, and still more preferably 3:7 to 7:3.

Further, as the component (S), a mixed solvent of at least one of PGMEAand EL with γ-butyrolactone is also preferable. The mixing ratio(former:latter) of such a mixed solvent is preferably from 70:30 to95:5.

The amount of the component (S) used is not particularly limited, and isappropriately adjusted to a concentration which enables coating of acoating solution to a substrate, depending on the thickness of thecoating film. In general, the component (S) is used in an amount suchthat the solid content of the resist composition is within the rangefrom 2 to 20% by weight, and preferably from 3 to 15% by weight.

<<Method of Forming a Resist Pattern>>

The method of forming a resist pattern according to the presentinvention includes: applying a positive resist composition of thepresent invention to a substrate to form a resist film on the substrate;subjecting the resist film to exposure; and developing the resist filmto form a resist pattern.

More specifically, the method for forming a resist pattern according tothe present invention can be performed, for example, as follows.Firstly, the resist composition is applied onto a substrate such as asilicon wafer using a spinner or the like, and a prebake (post appliedbake (PAB)) is conducted at 80 to 150° C. for 40 to 120 seconds,preferably 60 to 90 seconds to form a resist film. Then, for example,using an ArF exposure apparatus or the like, the resist film isselectively exposed to an ArF excimer laser beam through a desired maskpattern, followed by post exposure bake (PEB) at 80 to 150° C. for 40 to120 seconds, preferably 60 to 90 seconds. Subsequently, developing isconducted using an alkali developing solution such as a 0.1 to 10% byweight aqueous solution of tetramethylanunonium hydroxide. In thismanner, a resist pattern that is fail to the mask pattern can beobtained.

An organic or inorganic antireflection film may be provided between thesubstrate and the applied coating layer of the positive resistcomposition.

The wavelength to be used for exposure is not particularly limited andthe exposure can be conducted using radiations such as ArF excimerlaser, KrF excimer laser, F₂ excimer laser, extreme ultraviolet rays(EUV), vacuum ultraviolet rays (VUV), electron beam (EB), X-rays, andsoft X-rays. The positive resist composition of the present invention isparticularly effective to ArF excimer laser.

The positive resist composition and method of forming a resist patternaccording to the present invention is capable of achieving excellentsolubility in an organic solvent and forming a resist pattern having anexcellent shape.

Further, by the present invention, excellent lithography properties canbe achieved with respect to sensitivity, resolution, line widthroughness (LWR), mask error factor (MEF), exposure margin (EL margin),and the like.

The reason why the solubility in an organic solvent increases ispresumed as follows.

Conventionally, in a positive resist composition used for ArF excimerlaser lithography and the like, for the purpose of enhancing thecompatibility with the developing solution and improving the alkalisolubility of the exposed portions, a resin containing a polargroup-containing aliphatic hydrocarbon group, e.g., a structural unithaving the structure “—Y¹ (aliphatic cyclic group)-OH” have been used.However, such a resin containing a structural unit having the structure“—Y¹—OH” reduces the solubility of the resin in an organic solvent byits high hydrophilicity, and thus, the solubility of a positive resistcomposition containing such a resin in an organic solvent becomes poor.In contrast, the resin used in the present invention contains astructural unit (a0-1) having the structure “—Y″-(CH₂)_(e)—O-Z” (whereinY¹, e and Z are respectively as defined for Y¹, e and Z in generalformula (a0-1)). In this structure “—Y¹—(CH₂)_(e)—O-Z”, Z exhibits lowpolarity as compared to a hydrogen atom. Further, the molecular chain ofthis structure is relatively long. Therefore, it is presumed that thecompatibility of the component (A) for an organic solvent is enhanced,and the solubility of the component (A) is improved.

Further, in the present invention, the reason why a resist patternhaving an excellent shape can be formed is presumed that synergism ofthe structural unit (a0-1) with the structural unit (a0-2).

Furthermore, in the present invention, the same or higher level oflithography properties can be achieved by replacing a part or all of thestructural unit (a2) with the structural unit (a0-1). As a result, theamount of the structural unit (a2) can be reduced without changing theamount of the structural unit (a0-2). When the amount of the structuralunit (a0-2) is at the same level, the Tg of the component (A) becomeshigher as the amount of the structural unit (a2) becomes lower. It ispresumed that the increase of Tg contributes to suppressing thesoftening of the resist film during baking after exposure, suppressingthe diffusion of the acid generated upon exposure, and improvement inthe rectangularity of the resist pattern.

Moreover, in the present invention, a resist pattern having an excellentshape can be formed in which generation of defects is suppressed.

Conventionally, in the fields of lithography, a problem arises in thatdefects are generated on the surface of the formed resist pattern.“Defects” refers to general abnormalities of a resist pattern, which aredetected when observed from directly above the developed resist pattern,using, for example, surface defect detection equipment (trade name:“KLA”) manufactured by KLA-TENCOR CORPORATION. Examples of theseabnormalities include post-developing scum, foam, dust, bridges acrossdifferent portions of the resist pattern, color irregularities, andforeign deposits. Improvements in the defect problem are becoming moreand more important as the demand for resist patterns with higherresolution is increasing. Especially, in lithography techniques usingArF excimer lasers and lithography techniques developed thereafter suchas lithography techniques using F₂ excimer lasers, EUV, electron beam(EB) and the like as the light source, when a fine pattern such as aresist pattern of no more than 130 nm is formed, these defects arebecoming of serious problems.

One of the reasons for defects is presumed to be the poor solubility inan organic solvent and the low stability of the resist solution due tosuch poor solubility. The positive resist composition of the presentinvention exhibits excellent solubility in an organic solvent, and istherefore effective in solving the problems of defects.

EXAMPLES

As follows is a description of examples of the present invention,although the scope of the present invention is by no way limited bythese examples.

(A)-1 to (A)-7 used in Examples 1 to 7 and Comparative Example 1 weresynthesized in Synthesis Examples 2 to 9 by copolymerizing monomers (1)to (9) shown below (the production method of monomer (1) is shown below)by a conventional dropwise polymerization method.

In Synthesis Examples 2 to 9, Mw and Mw/Mn of (A)-1 to (A)-8 weremeasured by gel permeation chromatography (GPC).

In Synthesis Examples 2 to 9, each of the subscript numerals at thelower right of the brackets in formulas (A)-1 to (A)-8 indicate theamount (mol %) of the respective structural units.

Synthesis Example 1 Synthesis of Monomer (1)

150 mL of THF (tetrahydrofuran) were charged into an eggplant-shapedflask, and 20 g of the monomer (4) above(1-(3-hydroxyadamantyl)methacrylate) and 10 g of triethylamine wereadded thereto. Then, 22 g of t-butoxycarboxylic acid anhydride wereadded while cooling with ice, and the resultant was stirred at roomtemperature for 3 hours. Thereafter, the reaction liquid was subjectedto extraction with ethyl acetate, followed by concentration, therebyobtaining the monomer (1) above.

Synthesis Example 2

86 g of PGMEA were charged into a flask equipped with an inlet fornitrogen, a stirrer, a condenser and a thermometer in a nitrogenatmosphere, and the temperature of the water bath was elevated to 80° C.while stirring. A monomer solution obtained by mixing 17.3 g of monomer(1), 45.1 g of monomer (2), 30.6 g of monomer (3), 24.3 g of monomer(4), 154 g of PGMEA and 2.9 g of 2,2′-azobisisobutyronitrile (AIBN) wereadded dropwise into the flask using a dripping apparatus at a constantrate over 6 hours, and then the temperature was maintained at 80° C. for1 hour. Then, the temperature of the reaction liquid was cooled to roomtemperature. Subsequently, the resulting reaction liquid was addeddropwise to methanol about 30 times in amount while stirring, to obtaina colorless precipitate. The obtained precipitate was subjected tofiltration, and then the precipitate was washed in methanol in an amountabout 30 times the amount of the monomers used in the polymerization.The resulting precipitate was subjected to filtration, followed bydrying at 50° C., under reduced pressure for about 40 hours, therebyobtaining a resin (A)-1. The obtained resin (A)-1 was subjected to GPCmeasurement. As a result, it was found that the weight average molecularweight (Mw) was 7,000, and the dispersity (Mw/Mn) was 1.7.

Synthesis Example 3

86 g of PGMEA were charged into a flask equipped with an inlet fornitrogen, a stirrer, a condenser and a thermometer in a nitrogenatmosphere, and the temperature of the water bath was elevated to 80° C.while stirring. A monomer solution obtained by mixing 37.9 g of monomer(1), 49.3 g of monomer (2), 23.9 g of monomer (3), 26.6 g of monomer(4), 155 g of PGMEA and 3.2 g of 2,2′-azobisisobutyronitrile (AIBN) wereadded dropwise into the flask using a dripping apparatus at a constantrate over 6 hours, and then the temperature was maintained at 80° C. for1 hour. Then, the temperature of the reaction liquid was cooled to roomtemperature. Subsequently, the resulting reaction liquid was addeddropwise to methanol about 30 times in amount while stirring, to obtaina colorless precipitate. The obtained precipitate was subjected tofiltration, and then the precipitate was washed in methanol in an amountabout 30 times the amount of the monomers used in the polymerization.The resulting precipitate was subjected to filtration, followed bydrying at 50° C. under reduced pressure for about 40 hours, therebyobtaining a resin (A)-2.

The obtained resin (A)-2 was subjected to GPC measurement. As a result,it was found that the weight average molecular weight (Mw) was 7,000,and the dispersity (Mw/Mn) was 1.7.

Synthesis Example 4

86 g of PGMEA were charged into a flask equipped with an inlet fornitrogen, a stirrer, a condenser and a thermometer in a nitrogenatmosphere, and the temperature of the water bath was elevated to 80° C.while stirring A monomer solution obtained by mixing 17.9 g of monomer(1), 46.6 g of monomer (2), 40.7 g of monomer (3), 12.6 g of monomer(4), 155 g of PGMEA and 3.1 g of 2,2′-azobisisobutyronitrile (AIBN) wereadded dropwise into the flask using a dripping apparatus at a constantrate over 6 hours, and then the temperature was maintained at 80° C. for1 hour. Then, the temperature of the reaction liquid was cooled to roomtemperature. Subsequently, the resulting reaction liquid was addeddropwise to methanol about 30 times in amount while stirring, to obtaina colorless precipitate. The obtained precipitate was subjected tofiltration, and then the precipitate was washed in methanol in an amountabout 30 times the amount of the monomers used in the polymerization.The resulting precipitate was subjected to filtration, followed bydrying at 50° C. under reduced pressure for about 40 hours, therebyobtaining a resin (A)-3.

The obtained resin (A)-3 was subjected to GPC measurement. As a result,it was found that the weight average molecular weight (Mw) was 7,000,and the dispersity (Mw/Mn) was 1.7.

Synthesis Example 5

86 g of PGMEA were charged into a flask equipped with an inlet fornitrogen, a stirrer, a condenser and a thermometer in a nitrogenatmosphere, and the temperature of the water bath was elevated to 80° C.while stirring. A monomer solution obtained by mixing 41.4 g of monomer(2), 36.2 g of monomer (3), 22.3 g of monomer (4), 155 g of PGMEA and2.7 g of 2,2′-azobisisobutyronitrile (AIBN) were added dropwise into theflask using a dripping apparatus at a constant rate over 6 hours, andthen the temperature was maintained at 80° C. for 1 hour. Then, thetemperature of the reaction liquid was cooled to room temperature.Subsequently, the resulting reaction liquid was added dropwise tomethanol about 30 times in amount while stirring, to obtain a colorlessprecipitate. The obtained precipitate was subjected to filtration, andthen the precipitate was washed in methanol in an amount about 30 timesthe amount of the monomers used in the polymerization. The resultingprecipitate was subjected to filtration, followed by drying at 50° C.under reduced pressure for about 40 hours, thereby obtaining a resin(A)-4.

The obtained resin (A)-4 was subjected to GPC measurement. As a result,it was found that the weight average molecular weight (Mw) was 7,000,and the dispersity (Mw/Mn) was 1.5.

Synthesis Example 6

86 g of PGMEA were charged into a flask equipped with an inlet fornitrogen, a stirrer, a condenser and a thermometer in a nitrogenatmosphere, and the temperature of the water bath was elevated to 80° C.while stirring. A monomer solution obtained by mixing 20.4 g of monomer(1), 44.3 g of monomer (5), 41.4 g of monomer (3), 20.4 g of monomer(4), 155 g of PGMEA and 3.5 g of 2,2′-azobisisobutyronitrile (AIBN) wereadded dropwise into the flask using a dripping apparatus at a constantrate over 6 hours, and then the temperature was maintained at 80° C. for1 hour. Then, the temperature of the reaction liquid was cooled to roomtemperature. Subsequently, the resulting reaction liquid was addeddropwise to methanol about 30 times in amount while stirring, to obtaina colorless precipitate. The obtained precipitate was subjected tofiltration, and then the precipitate was washed in methanol in an amountabout 30 times the amount of the monomers used in the polymerization.The resulting precipitate was subjected to filtration, followed bydrying at 50° C. under reduced pressure for about 40 hours, therebyobtaining a resin (A)-5.

The obtained resin (A)-5 was subjected to GPC measurement. As a result,it was found that the weight average molecular weight (Mw) was 10,000,and the dispersity (Mw/Mn) was 1.7.

Synthesis Example 7

86 g of PGMEA were charged into a flask equipped with an inlet fornitrogen, a stirrer, a condenser and a thermometer in a nitrogenatmosphere, and the temperature of the water bath was elevated to 80° C.while stirring. A monomer solution obtained by mixing 18.1 g of monomer(1), 53.8 g of monomer (2), 33.5 g of monomer (8), 12.7 g of monomer(4), 155 g of PGMEA and 3.1 g of 2,2′-azobisisobutyronitrile (AIBN) wereadded dropwise into the flask using a dripping apparatus at a constantrate over 6 hours, and then the temperature was maintained at 80° C. for1 hour. Then, the temperature of the reaction liquid was cooled to roomtemperature. Subsequently, the resulting reaction liquid was addeddropwise to methanol about 30 times in amount while stirring, to obtaina colorless precipitate. The obtained precipitate was subjected tofiltration, and then the precipitate was washed in methanol in an amountabout 30 times the amount of the monomers used in the polymerization.The resulting precipitate was subjected to filtration, followed bydrying at 50° C. under reduced pressure for about 40 hours, therebyobtaining a resin (A)-6.

The obtained resin (A)-6 was subjected to GPC measurement. As a result,it was found that the weight average molecular weight (Mw) was 10,000,and the dispersity (Mw/Mn) was 1.7.

Synthesis Example 8

86 g of PGMEA were charged into a flask equipped with an inlet fornitrogen, a stirrer, a condenser and a thermometer in a nitrogenatmosphere, and the temperature of the water bath was elevated to 80° C.while stirring. A monomer solution obtained by mixing 15.8 g of monomer(1), 52.9 g of monomer (6), 35.9 g of monomer (3), 11.1 g of monomer(4), 155 g of PGMEA and 2.7 g of 2,2′-azobisisobutyronitrile (AIBN) wereadded dropwise into the flask using a dripping apparatus at a constantrate over 6 hours, and then the temperature was maintained at 80° C. for1 hour. Then, the temperature of the reaction liquid was cooled to roomtemperature. Subsequently, the resulting reaction liquid was addeddropwise to methanol about 30 times in amount while stirring, to obtaina colorless precipitate. The obtained precipitate was subjected tofiltration, and then the precipitate was washed in methanol in an amountabout 30 times the amount of the monomers used in the polymerization.The resulting precipitate was subjected to filtration, followed bydrying at 50° C. under reduced pressure for about 40 hours, therebyobtaining a resin (A)-7.

The obtained resin (A)-7 was subjected to GPC measurement. As a result,it was found that the weight average molecular weight (Mw) was 7,000,and the dispersity (Mw/Mn) was 1.6.

Synthesis Example 9

86 g of PGMEA were charged into a flask equipped with an inlet fornitrogen, a stirrer, a condenser and a thermometer in a nitrogenatmosphere, and the temperature of the water bath was elevated to 80° C.while stirring. A monomer solution obtained by mixing 25.7 g of monomer(1), 37.9 g of monomer (7), 36.4 g of monomer (9), 155 g of PGMEA and2.1 g of 2,2′-azobisisobutyronitrile (AIBN) were added dropwise into theflask using a dripping apparatus at a constant rate over 6 hours, andthe temperature was maintained at 80° C. for 1 hour. Then, thetemperature of the reaction liquid was cooled to room temperature.Subsequently, the resulting reaction liquid was added dropwise tomethanol about 30 times in amount while stirring, to obtain a colorlessprecipitate. The obtained precipitate was subjected to filtration, andthen the precipitate was washed in methanol in an amount about 30 timesthe amount of the monomers used in the polymerization. The resultingprecipitate was subjected to filtration, followed by drying at 50° C.under reduced pressure for about 40 hours, thereby obtaining a resin(A)-8. The obtained resin (A)-8 was subjected to GPC measurement. As aresult, it was found that the weight average molecular weight (Mw) was10,000, and the dispersity (Mw/Mn) was 1.6.

<<Evaluation of Solubility in Organic Solvent>>

With respect to resins (A)-1 to (A)-4, the solubility thereof in anorganic solvent was evaluated in the following manner.

As the organic solvent, a mixed solvent of PGMEA/PGME=6/4 (weight ratio)was used, and each of (A)-1 to (A)-4 was dissolved in an amount of 1 gin 12 g of the mixed solvent (23° C.).

As a result, it was found that (A)-1 to (A)-3 dissolved instantly afterthey were added to the mixed solvent.

On the other hand, (A)-4 could not be easily dissolved. Even when themixed solvent was stirred while subjecting to a ultrasonic wavetreatment, about 30 minutes was necessary for (A)-4 to be completelydissolved.

In each of (A)-1 and (A)-2, the amount of the structural unit derivedfrom the monomer (4) was the same as that in (A)-4, i.e., the amount ofhydroxyl groups contained in each of (A)-1 and (A)-2 was the same asthat in (A)-4. Nevertheless, (A)-1 and (A)-2 exhibited an excellentsolubility in an organic solvent.

Further, (A)-3 is a resin in which a half of the structural unit derivedfrom the monomer (4) within (A)-4 have been replaced by the structuralunit derived from the monomer (1). Like (A)-1 and (A)-2, (A)-3 exhibitedan excellent solubility in an organic solvent.

Subsequently, with respect to each of resins (A)-5 to (A)-8, a mixtureof (A)-5 and (A)-7 ((A)-5:(A)-7=50:50 (weight ratio)) and a mixture of(A)-6 and (A)-8 ((A)-6:(A)-8=50:50 (weight ratio)), the solubilitythereof in an organic solvent was evaluated in the same manner asdescribed above.

As a result, it was found that each of the resins exhibited an excellentsolubility in an organic solvent.

Examples 1 to 7 Comparative Example 1

The components shown in Table 1 were mixed together and dissolved toobtain positive resist compositions.

TABLE 1 Component (A) Component (B) Component (D) Component (E)Component (S) Example 1 (A)-1 — (B)-1 — (D)-1 (E)-1 (S)-1 (S)-2 [100][13.0] [0.54] [1.32] [10.0] [2000] Example 2 (A)-2 — (B)-1 — (D)-1 (E)-1(S)-1 (S)-2 [100] [13.0] [0.54] [1.32] [10.0] [2000] Example 3 (A)-3 —(B)-1 — (D)-1 (E)-1 (S)-1 (S)-2 [100] [13.0] [0.54] [1.32] [10.0] [2000]Example 4 (A)-4 (A)-6 (B)-1 (B)-2 (D)-1 (E)-1 — (S)-2  [50] [50]  [6.0][4.0] [0.40] [1.50] [2000] Example 5 (A)-4 (A)-6 (B)-3 (B)-4 (D)-1 (E)-1— (S)-2  [50] [50]  [3.0] [5.0] [0.40] [1.50] [2000] Example 6 (A)-5(A)-7 (B)-1 (B)-2 (D)-1 (E)-1 — (S)-2  [50] [50]  [6.0] [4.0] [0.40][1.50] [2000] Example 7 (A)-3 (A)-7 (B)-1 (B)-2 (D)-1 (E)-1 — (S)-2 [50] [50]  [6.0] [4.0] [0.40] [1.50] [2000] Comparative (A)-4 (B)-1 —(D)-1 (E)-1 (S)-1 (S)-2 Example 1 [100] [13.0] [0.54] [1.32] [10.0][2000] In Table 1, the reference characters indicate the following.Further, the values in brackets [ ] indicate the amount (in terms ofparts by weight) of the component added. (B)-1: a compound representedby formula (B)-1 shown below (B)-2: a compound represented by formula(B)-2 shown below (B)-3: a compound represented by formula (B)-3 shownbelow (B)-4: a compound represented by formula (B)-4 shown below (D)-1:tri-n-pentylamine (E)-1: salicylic acid (S)-1: γ-butyrolactone (S)-2: amixed solvent of PGMEA/PGME = 6/4 (weight ratio)

With respect to each of the positive resist compositions, a resistpattern was formed in the following manner, and lithography propertieswere evaluated.

An organic anti-reflection film composition (product name: ARC-29A,manufactured by Brewer Science Ltd.) was applied onto an 8-inch siliconwafer using a spinner, and the composition was then baked at 205° C. for60 seconds, thereby forming an organic anti-reflection film having afilm thickness of 77 nm. Then, a positive resist composition was appliedonto the anti-reflection film using a spinner, and was then prebaked(PAB) on a hotplate at a temperature indicated in Table 2 for 60 secondsand dried, thereby forming a resist film having a film thickness of 150nm.

Subsequently, the resist film was selectively irradiated with an ArFexcimer laser (193 nm) through a mask pattern (6% half tone rectile),using an ArF exposure apparatus NSR—S-302 (manufactured by NikonCorporation, NA (numerical aperture)=0.60, ⅔ annular illumination).Thereafter, a post exposure bake (PEB) treatment was conducted at thetemperature indicated in Table 2 for 60 seconds, followed by developmentfor 30 seconds at 23° C. in a 2.38% by weight aqueous solution oftetramethylammonium hydroxide (TMAH). Then, the resist was washed for 30seconds with pure water, followed by drying by shaking.

As a result, in each of the examples using the respective positiveresist compositions, a line and space pattern (hereafter referred to as“LS pattern”) having a line width of 120 nm and a pitch of 240 nm wasformed.

<Evaluation of Sensitivity>

In the evaluation of pattern formability described above, the optimumexposure dose (Eop) (unit: mJ/cm² (amount of energy per unit area)) withwhich a LS pattern having a line width of 120 nm and a pitch of 240 mmwas formed was determined. As a result, it was found that the Eop wassubstantially the same in Examples 1 to 7 and Comparative Example 1.

<Evaluation of Resolution>

With the above Eop, LS patterns were formed in the same manner asdescribed above, except that the mask size was changed so as to targetLS patterns with line widths of 140 nm, 130 mm, 120 nm and 110 nm(wherein the ratio of the line width to the space width was 1:1).

As a result, in each of Examples 1 to 7 and Comparative Example 1, a LSpattern having a line width of 110 nm and a pitch of 220 nm could beresolved.

<Evaluation of Pattern Shape>

The cross-sectional shape of the LS patterns formed in the evaluation ofresolution above were observed using a measuring SEM (product name:S-9220, manufactured by Hitachi, Ltd.).

As a result, with respect to the LS patterns formed in Examples 1 to 7,it was found that the perpendicularity of the side walls of the patternswas high, and the patterns exhibited high rectangularity, and hence, thecross-sectional shape was excellent.

On the other hand, with respect to the LS pattern formed in ComparativeExample 1, it was found that the cross-sectional shape was slightlytapered, and the rectangularity was low. Further, with respect to the LSpattern having a line width of 110 nm and a pitch of 220 nm, the exposedportions were not completely removed, and hence, the removability of thepattern was unsatisfactory.

<Evaluation of Line Width Roughness (LWR)>

With respect to a LS pattern having a line width of 120 nm and a pitchof 240 nm formed with the above Eop, 5 points in the lengthwisedirection of the line were measured using a measuring SEM (product name:S-9220, manufactured by Hitachi, Ltd.; measurement voltage: 300V), andfrom the results, the value of 3 times the standard deviation s (3 s;unit: nm) was calculated as a yardstick of LWR. The results are shown inTable 2. The smaller this 3 s value is, the lower the level of roughnessof the line width, indicating that a resist pattern with a uniform widthwas obtained.

As seen from the results shown in Table 2, in Examples 1 to 7, the LWRwas about the same or higher level as the LWR in Comparative Example 1.Especially, in Examples 4 and 5 in which the resin (A)-4 and the resin(A)-6 were used in combination, the LWR was particularly good. Further,in Example 6 in which the resin (A)-5 and the resin (A)-7 were used incombination, the LWR was good.

TABLE 2 PAB temperature PEB temperature LWR (C. °) (C. °) (nm) Example 1105 105 10.4 Example 2 105 105 9.9 Example 3 105 105 9.6 Example 4 110110 7.8 Example 5 110 110 9.1 Example 6 105 100 9.5 Example 7 105 10010.2 Comparative 105 105 10.3 Example 1

<Evaluation of Mask Error Factor (MEF)>

With the above-mentioned Eop, LS patterns were formed using a maskpattern targeting a LS pattern having a line width of 130 nm and a pitchof 260 nm and a mask pattern targeting a LS pattern having a line widthof 120 nm and a pitch of 260 nm. With respect to the formed LS patterns,the MEF was determined by the following formula.

MEF=|CD ₁₃₀ −CD ₁₂₀ |/|MD ₁₃₀ −MD ₁₂₀|

In this formula, CD₁₃₀ and CD₁₂₀ represent the respective line widths(nm) of the actual LS patterns respectively formed using the maskpattern targeting a line width of 130 nm and the mask pattern targetinga line width of 120 nm, and MD₁₃₀ and MD₁₂₀ represent the respectivetarget line widths (nm), meaning MD₁₃₀=130 and MD₁₂₀=120. The closer theMEF value is to 1, the better the mask reproducibility of the resistpattern formed.

As a result, it was found that in each of Examples 1 to 7 andComparative Example 1, the MEF was about the same level.

<Evaluation of Mask Linearity>

With the above Eop, the LS ratio (ratio of the line width to the spacewidth) of the mask pattern was fixed to 1:1, and the mask size (linewidth) was changed to 110 nm, 120 nm, 130 nm, 140 nm and 150 nm, to formLS patterns. The size (line width) of the formed LS patterns wasmeasured. The closer the resist pattern size measured is to the masksize, i.e., the smaller the difference between the resist pattern sizemeasured and the mask size is, it indicates that a resist patternfaithful to the mask pattern was formed. As a result, it was found thatin each of Examples 1 to 7 and Comparative Example 1, the mask linearitywas about the same level.

<Evaluation of Exposure Margin (EL Margin)>

Using a mask pattern targeting a LS pattern having a line width of 120nm and a pitch of 240 nm, a LS pattern was formed while changing theexposure dose within the range of the above Eop±5%, and the variation inthe line width of the LS pattern per exposure dose of 1 mJ (unit: nm/mJ)was determined.

The larger this variation (EL margin) is, the smaller the variation inthe pattern size depending on the variation in the exposure dose.

As a result, it was found that in each of Examples 1 to 7 andComparative Example 1, the EL margin was about the same level.

As seen from the results shown above, in each of Examples 1 to 7 inwhich the positive resist composition of the present invention was used,the component (A) used exhibited an extremely high solubility in anorganic solvent, and a resist pattern having an excellent shape could beformed. Further, in Examples 1 to 7, various lithography properties(sensitivity, resolution, LWR, MEF, EL, and the like) were the same orhigher level as that in Comparative Example 1.

On the other hand, in Comparative Example 1, the solubility of thecomponent (A) in an organic solvent was poor, and the rectangularity ofthe resist pattern was low.

INDUSTRIAL APPLICABILITY

According to the present invention, there are provided a positive resistcomposition which exhibits excellent solubility in an organic solventand is capable of forming a resist pattern having an excellent shape,and a method of forming a resist pattern. Therefore, the presentinvention is extremely useful in industry.

1. A positive resist composition comprising a resin component (A) whichexhibits increased alkali solubility under action of acid and anacid-generator component (B) which generates acid upon exposure, saidresin component (A) comprising a structural unit (a0-1) represented bygeneral formula (a0-1) shown below and a structural unit (a0-2)represented by general formula (a0-2) shown below:

wherein: in general formula (a0-1), R represents a hydrogen atom, ahalogen atom, a lower alkyl group or a halogenated lower alkyl group; Y¹represents an aliphatic cyclic group; Z represents a tertiary alkylgroup-containing group or an alkoxyalkyl group; a represents an integerof 1 to 3, and b represents an integer of 0 to 2, with the proviso thata+b=1 to 3; and each of c, d and e independently represents an integerof 0 to 3, and in general formula (a0-2), R represents a hydrogen atom,a halogen atom, a lower alkyl group or a halogenated lower alkyl group;Y³ represents an aliphatic cyclic group; each of g and h independentlyrepresents an integer of 0 to 3; and i represents an integer of 1 to 3.2. The positive resist composition according to claim 1, wherein theamount of said structural unit (a0-1) within said resin component (A),based on the combined total of all structural units constituting saidresin component (A) is 1 to 40 mol %.
 3. The positive resist compositionaccording to claim 1, wherein said resin component (A) further comprisesa structural unit (a1) derived from an acrylate ester having an aciddissociable, dissolution inhibiting group.
 4. The positive resistcomposition according to claim 1, wherein said resin component (A)further comprises a structural unit (a2) derived from an acrylate esterhaving a lactone-containing cyclic group.
 5. The positive resistcomposition according to claim 3, wherein said resin component (A)further comprises a structural unit (a2) derived from an acrylate esterhaving a lactone-containing cyclic group.
 6. The positive resistcomposition according to claim 1, which further comprises anitrogen-containing organic compound (D).
 7. A method of forming aresist pattern, comprising: applying a positive resist composition ofany one of claim 1 to 6 to a substrate to form a resist film on thesubstrate; subjecting said resist film to exposure; and developing saidresist film to form a resist pattern.